Using the GNU Privacy Guard

This is the The GNU Privacy Guard Manual (version 2.1.15, August 2016).

© 2002, 2004, 2005, 2006, 2007, 2010 Free Software Foundation, Inc.
© 2013, 2014, 2015 Werner Koch.
© 2015 g10 Code GmbH.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version. The text of the license can be found in the section entitled “Copying”.

This manual documents how to use the GNU Privacy Guard system as well as the administration and the architecture.

Short Table of Contents

Table of Contents

1 A short installation guide.

Unfortunately the installation guide has not been finished in time. Instead of delaying the release of GnuPG 2.0 even further, I decided to release without that guide. The chapter on gpg-agent and gpgsm do include brief information on how to set up the whole thing. Please watch the GnuPG website for updates of the documentation. In the meantime you may search the GnuPG mailing list archives or ask on the gnupg-users mailing listsfor advise on how to solve problems or how to get that whole thing up and running.

** Building the software

Building the software is decribed in the file INSTALL. Given that you are already reading this documentation we can only give some extra hints

To comply with the rules on GNU systems you should have build time configured gnupg using:

./configure --sysconfdir=/etc --localstatedir=/var

This is to make sure that system wide configuration files are searched in the directory /etc and variable data below /var; the default would be to also install them below /usr/local where the binaries get installed. If you selected to use the --prefix=/ you obviously don’t need those option as they are the default then.

** Notes on setting a root CA key to trusted

X.509 is based on a hierarchical key infrastructure. At the root of the tree a trusted anchor (root certificate) is required. There are usually no other means of verifying whether this root certificate is trustworthy than looking it up in a list. GnuPG uses a file (trustlist.txt) to keep track of all root certificates it knows about. There are 3 ways to get certificates into this list:

• Use the list which comes with GnuPG. However this list only contains a few root certificates. Most installations will need more.
• Let gpgsm ask you whether you want to insert a new root certificate. This feature is enabled by default; you may disable it using the option no-allow-mark-trusted into gpg-agent.conf.
• Manually maintain the list of trusted root certificates. For a multi user installation this can be done once for all users on a machine. Specific changes on a per-user base are also possible.

2 Invoking GPG-AGENT

gpg-agent is a daemon to manage secret (private) keys independently from any protocol. It is used as a backend for gpg and gpgsm as well as for a couple of other utilities.

The agent is automatically started on demand by gpg, gpgsm, gpgconf, or gpg-connect-agent. Thus there is no reason to start it manually. In case you want to use the included Secure Shell Agent you may start the agent using:

gpg-connect-agent /bye

You should always add the following lines to your .bashrc or whatever initialization file is used for all shell invocations:

GPG_TTY=$(tty)
export GPG_TTY

It is important that this environment variable always reflects the output of the tty command. For W32 systems this option is not required.

Please make sure that a proper pinentry program has been installed under the default filename (which is system dependent) or use the option pinentry-program to specify the full name of that program. It is often useful to install a symbolic link from the actual used pinentry (e.g. /usr/bin/pinentry-gtk) to the expected one (e.g. /usr/bin/pinentry).

See Option Index,for an index to GPG-AGENT’s commands and options.

2.1 Commands

Commands are not distinguished from options except for the fact that only one command is allowed.

--version

Print the program version and licensing information. Note that you cannot abbreviate this command.

--help

-h

Print a usage message summarizing the most useful command-line options. Note that you cannot abbreviate this command.

--dump-options

Print a list of all available options and commands. Note that you cannot abbreviate this command.

--server

Run in server mode and wait for commands on the stdin. The default mode is to create a socket and listen for commands there.

--daemon [command line]

Start the gpg-agent as a daemon; that is, detach it from the console and run it in the background.

As an alternative you may create a new process as a child of gpg-agent: gpg-agent --daemon /bin/sh. This way you get a new shell with the environment setup properly; after you exit from this shell, gpg-agent terminates within a few seconds.

2.2 Option Summary

--options file

Reads configuration from file instead of from the default per-user configuration file. The default configuration file is named gpg-agent.conf and expected in the .gnupg directory directly below the home directory of the user.

--homedir dir

Set the name of the home directory to dir. If this option is not used, the home directory defaults to ~/.gnupg. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable GNUPGHOME or (on Windows systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

On Windows systems it is possible to install GnuPG as a portable application. In this case only this command line option is considered, all other ways to set a home directory are ignored.

To install GnuPG as a portable application under Windows, create an empty file name gpgconf.ctl in the same directory as the tool gpgconf.exe. The root of the installation is than that directory; or, if gpgconf.exe has been installed directly below a directory named bin, its parent directory. You also need to make sure that the following directories exist and are writable: ROOT/home for the GnuPG home and ROOT/usr/var/cache/gnupg for internal cache files.

-v

--verbose

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to gpgsm, such as ‘-vv’.

-q

--quiet

Try to be as quiet as possible.

--batch

Don’t invoke a pinentry or do any other thing requiring human interaction.

--faked-system-time epoch

This option is only useful for testing; it sets the system time back or forth to epoch which is the number of seconds elapsed since the year 1970.

--debug-level level

Select the debug level for investigating problems. level may be a numeric value or a keyword:

none

No debugging at all. A value of less than 1 may be used instead of the keyword.

basic

Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

advanced

More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

expert

Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

guru

All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

--debug flags

This option is only useful for debugging and the behaviour may change at any time without notice. FLAGS are bit encoded and may be given in usual C-Syntax. The currently defined bits are:

0 (1)

X.509 or OpenPGP protocol related data

1 (2)

values of big number integers

2 (4)

low level crypto operations

5 (32)

memory allocation

6 (64)

caching

7 (128)

show memory statistics.

9 (512)

write hashed data to files named dbgmd-000*

10 (1024)

trace Assuan protocol

12 (4096)

bypass all certificate validation

--debug-all

Same as --debug=0xffffffff

--debug-wait n

When running in server mode, wait n seconds before entering the actual processing loop and print the pid. This gives time to attach a debugger.

--debug-quick-random

This option inhibits the use of the very secure random quality level (Libgcrypt’s GCRY_VERY_STRONG_RANDOM) and degrades all request down to standard random quality. It is only used for testing and should not be used for any production quality keys. This option is only effective when given on the command line.

On GNU/Linux, another way to quickly generate insecure keys is to use rngd to fill the kernel’s entropy pool with lower quality random data. rngd is typically provided by the rng-tools package. It can be run as follows: ‘sudo rngd -f -r /dev/urandom’.

--debug-pinentry

This option enables extra debug information pertaining to the Pinentry. As of now it is only useful when used along with --debug 1024.

--no-detach

Don’t detach the process from the console. This is mainly useful for debugging.

-s

--sh

-c

--csh

Format the info output in daemon mode for use with the standard Bourne shell or the C-shell respectively. The default is to guess it based on the environment variable SHELL which is correct in almost all cases.

--no-grab

Tell the pinentry not to grab the keyboard and mouse. This option should in general not be used to avoid X-sniffing attacks.

--log-file file

Append all logging output to file. This is very helpful in seeing what the agent actually does. If neither a log file nor a log file descriptor has been set on a Windows platform, the Registry entry HKCU\Software\GNU\GnuPG:DefaultLogFile, if set, is used to specify the logging output.

--no-allow-mark-trusted

Do not allow clients to mark keys as trusted, i.e. put them into the trustlist.txt file. This makes it harder for users to inadvertently accept Root-CA keys.

--allow-preset-passphrase

This option allows the use of gpg-preset-passphrase to seed the internal cache of gpg-agent with passphrases.

--no-allow-loopback-pinentry

--allow-loopback-pinentry

Disallow or allow clients to use the loopback pinentry features; see the option pinentry-mode for details. Allow is the default.

The --force option of the Assuan command DELETE_KEY is also controlled by this option: The option is ignored if a loopback pinentry is disallowed.

--no-allow-external-cache

Tell Pinentry not to enable features which use an external cache for passphrases.

Some desktop environments prefer to unlock all credentials with one master password and may have installed a Pinentry which employs an additional external cache to implement such a policy. By using this option the Pinentry is advised not to make use of such a cache and instead always ask the user for the requested passphrase.

--allow-emacs-pinentry

Tell Pinentry to allow features to divert the passphrase entry to a running Emacs instance. How this is exactly handled depends on the version of the used Pinentry.

--ignore-cache-for-signing

This option will let gpg-agent bypass the passphrase cache for all signing operation. Note that there is also a per-session option to control this behaviour but this command line option takes precedence.

--default-cache-ttl n

Set the time a cache entry is valid to n seconds. The default is 600 seconds. Each time a cache entry is accessed, the entry’s timer is reset. To set an entry’s maximum lifetime, use max-cache-ttl.

--default-cache-ttl-ssh n

Set the time a cache entry used for SSH keys is valid to n seconds. The default is 1800 seconds. Each time a cache entry is accessed, the entry’s timer is reset. To set an entry’s maximum lifetime, use max-cache-ttl-ssh.

--max-cache-ttl n

Set the maximum time a cache entry is valid to n seconds. After this time a cache entry will be expired even if it has been accessed recently or has been set using gpg-preset-passphrase. The default is 2 hours (7200 seconds).

--max-cache-ttl-ssh n

Set the maximum time a cache entry used for SSH keys is valid to n seconds. After this time a cache entry will be expired even if it has been accessed recently or has been set using gpg-preset-passphrase. The default is 2 hours (7200 seconds).

--enforce-passphrase-constraints

Enforce the passphrase constraints by not allowing the user to bypass them using the “Take it anyway” button.

--min-passphrase-len n

Set the minimal length of a passphrase. When entering a new passphrase shorter than this value a warning will be displayed. Defaults to 8.

--min-passphrase-nonalpha n

Set the minimal number of digits or special characters required in a passphrase. When entering a new passphrase with less than this number of digits or special characters a warning will be displayed. Defaults to 1.

--check-passphrase-pattern file

Check the passphrase against the pattern given in file. When entering a new passphrase matching one of these pattern a warning will be displayed. file should be an absolute filename. The default is not to use any pattern file.

Security note: It is known that checking a passphrase against a list of pattern or even against a complete dictionary is not very effective to enforce good passphrases. Users will soon figure up ways to bypass such a policy. A better policy is to educate users on good security behavior and optionally to run a passphrase cracker regularly on all users passphrases to catch the very simple ones.

--max-passphrase-days n

Ask the user to change the passphrase if n days have passed since the last change. With --enforce-passphrase-constraints set the user may not bypass this check.

--enable-passphrase-history

This option does nothing yet.

--pinentry-invisible-char char

This option asks the Pinentry to use char for displaying hidden characters. char must be one character UTF-8 string. A Pinentry may or may not honor this request.

--pinentry-timeout n

This option asks the Pinentry to timeout after n seconds with no user input. The default value of 0 does not ask the pinentry to timeout, however a Pinentry may use its own default timeout value in this case. A Pinentry may or may not honor this request.

--pinentry-program filename

Use program filename as the PIN entry. The default is installation dependent. With the default configuration the name of the default pinentry is pinentry; if that file does not exist but a pinentry-basic exist the latter is used.

On a Windows platform the default is to use the first existing program from this list: bin\pinentry.exe, ..\Gpg4win\bin\pinentry.exe, ..\Gpg4win\pinentry.exe, ..\GNU\GnuPG\pinentry.exe, ..\GNU\bin\pinentry.exe, bin\pinentry-basic.exe where the file names are relative to the GnuPG installation directory.

--pinentry-touch-file filename

By default the filename of the socket gpg-agent is listening for requests is passed to Pinentry, so that it can touch that file before exiting (it does this only in curses mode). This option changes the file passed to Pinentry to filename. The special name /dev/null may be used to completely disable this feature. Note that Pinentry will not create that file, it will only change the modification and access time.

--scdaemon-program filename

Use program filename as the Smartcard daemon. The default is installation dependent and can be shown with the gpgconf command.

--disable-scdaemon

Do not make use of the scdaemon tool. This option has the effect of disabling the ability to do smartcard operations. Note, that enabling this option at runtime does not kill an already forked scdaemon.

--disable-check-own-socket

gpg-agent employs a periodic self-test to detect a stolen socket. This usually means a second instance of gpg-agent has taken over the socket and gpg-agent will then terminate itself. This option may be used to disable this self-test for debugging purposes.

--use-standard-socket

--no-use-standard-socket

--use-standard-socket-p

Since GnuPG 2.1 the standard socket is always used. These options have no more effect. The command gpg-agent --use-standard-socket-p will thus always return success.

--display string

--ttyname string

--ttytype string

--lc-ctype string

--lc-messages string

--xauthority string

These options are used with the server mode to pass localization information.

--keep-tty

--keep-display

Ignore requests to change the current tty or X window system’s DISPLAY variable respectively. This is useful to lock the pinentry to pop up at the tty or display you started the agent.

--extra-socket name

Also listen on native gpg-agent connections on the given socket. The intended use for this extra socket is to setup a Unix domain socket forwarding from a remote machine to this socket on the local machine. A gpg running on the remote machine may then connect to the local gpg-agent and use its private keys. This enables decrypting or signing data on a remote machine without exposing the private keys to the remote machine.

--enable-ssh-support

--enable-putty-support

Enable the OpenSSH Agent protocol.

In this mode of operation, the agent does not only implement the gpg-agent protocol, but also the agent protocol used by OpenSSH (through a separate socket). Consequently, it should be possible to use the gpg-agent as a drop-in replacement for the well known ssh-agent.

SSH Keys, which are to be used through the agent, need to be added to the gpg-agent initially through the ssh-add utility. When a key is added, ssh-add will ask for the password of the provided key file and send the unprotected key material to the agent; this causes the gpg-agent to ask for a passphrase, which is to be used for encrypting the newly received key and storing it in a gpg-agent specific directory.

Once a key has been added to the gpg-agent this way, the gpg-agent will be ready to use the key.

Note: in case the gpg-agent receives a signature request, the user might need to be prompted for a passphrase, which is necessary for decrypting the stored key. Since the ssh-agent protocol does not contain a mechanism for telling the agent on which display/terminal it is running, gpg-agent’s ssh-support will use the TTY or X display where gpg-agent has been started. To switch this display to the current one, the following command may be used:

gpg-connect-agent updatestartuptty /bye

Although all GnuPG components try to start the gpg-agent as needed, this is not possible for the ssh support because ssh does not know about it. Thus if no GnuPG tool which accesses the agent has been run, there is no guarantee that ssh is able to use gpg-agent for authentication. To fix this you may start gpg-agent if needed using this simple command:

gpg-connect-agent /bye

Adding the --verbose shows the progress of starting the agent.

The --enable-putty-support is only available under Windows and allows the use of gpg-agent with the ssh implementation putty. This is similar to the regular ssh-agent support but makes use of Windows message queue as required by putty.

All the long options may also be given in the configuration file after stripping off the two leading dashes.

2.3 Configuration

There are a few configuration files needed for the operation of the agent. By default they may all be found in the current home directory (see option --homedir).

gpg-agent.conf

This is the standard configuration file read by gpg-agent on startup. It may contain any valid long option; the leading two dashes may not be entered and the option may not be abbreviated. This file is also read after a SIGHUP however only a few options will actually have an effect. This default name may be changed on the command line (see option --options). You should backup this file.

trustlist.txt

This is the list of trusted keys. You should backup this file.

Comment lines, indicated by a leading hash mark, as well as empty lines are ignored. To mark a key as trusted you need to enter its fingerprint followed by a space and a capital letter S. Colons may optionally be used to separate the bytes of a fingerprint; this enables cutting and pasting the fingerprint from a key listing output. If the line is prefixed with a ! the key is explicitly marked as not trusted.

Here is an example where two keys are marked as ultimately trusted and one as not trusted:

# CN=Wurzel ZS 3,O=Intevation GmbH,C=DE A6935DD34EF3087973C706FC311AA2CCF733765B S # CN=PCA-1-Verwaltung-02/O=PKI-1-Verwaltung/C=DE DC:BD:69:25:48:BD:BB:7E:31:6E:BB:80:D3:00:80:35:D4:F8:A6:CD S # CN=Root-CA/O=Schlapphuete/L=Pullach/C=DE !14:56:98:D3:FE:9C:CA:5A:31:6E:BC:81:D3:11:4E:00:90:A3:44:C2 S

Before entering a key into this file, you need to ensure its authenticity. How to do this depends on your organisation; your administrator might have already entered those keys which are deemed trustworthy enough into this file. Places where to look for the fingerprint of a root certificate are letters received from the CA or the website of the CA (after making 100% sure that this is indeed the website of that CA). You may want to consider disallowing interactive updates of this file by using the See option --no-allow-mark-trusted. It might even be advisable to change the permissions to read-only so that this file can’t be changed inadvertently.

As a special feature a line include-default will include a global list of trusted certificates (e.g. /usr/etc/gnupg/trustlist.txt). This global list is also used if the local list is not available.

It is possible to add further flags after the S for use by the caller:

relax

Relax checking of some root certificate requirements. As of now this flag allows the use of root certificates with a missing basicConstraints attribute (despite that it is a MUST for CA certificates) and disables CRL checking for the root certificate.

cm

If validation of a certificate finally issued by a CA with this flag set fails, try again using the chain validation model.

sshcontrol

This file is used when support for the secure shell agent protocol has been enabled (see option --enable-ssh-support). Only keys present in this file are used in the SSH protocol. You should backup this file.

The ssh-add tool may be used to add new entries to this file; you may also add them manually. Comment lines, indicated by a leading hash mark, as well as empty lines are ignored. An entry starts with optional whitespace, followed by the keygrip of the key given as 40 hex digits, optionally followed by the caching TTL in seconds and another optional field for arbitrary flags. A non-zero TTL overrides the global default as set by --default-cache-ttl-ssh.

The only flag support is confirm. If this flag is found for a key, each use of the key will pop up a pinentry to confirm the use of that key. The flag is automatically set if a new key was loaded into gpg-agent using the option -c of the ssh-add command.

The keygrip may be prefixed with a ! to disable an entry entry.

The following example lists exactly one key. Note that keys available through a OpenPGP smartcard in the active smartcard reader are implicitly added to this list; i.e. there is no need to list them.

# Key added on: 2011-07-20 20:38:46 # Fingerprint: 5e:8d:c4:ad:e7:af:6e:27:8a:d6:13:e4:79:ad:0b:81 34B62F25E277CF13D3C6BCEBFD3F85D08F0A864B 0 confirm

private-keys-v1.d/

This is the directory where gpg-agent stores the private keys. Each key is stored in a file with the name made up of the keygrip and the suffix key. You should backup all files in this directory and take great care to keep this backup closed away.

Note that on larger installations, it is useful to put predefined files into the directory /usr/etc/skel/.gnupg so that newly created users start up with a working configuration. For existing users the a small helper script is provided to create these files (see addgnupghome).

2.4 Use of some signals.

A running gpg-agent may be controlled by signals, i.e. using the kill command to send a signal to the process.

Here is a list of supported signals:

SIGHUP

This signal flushes all cached passphrases and if the program has been started with a configuration file, the configuration file is read again. Only certain options are honored: quiet, verbose, debug, debug-all, debug-level, debug-pinentry, no-grab, pinentry-program, pinentry-invisible-char, default-cache-ttl, max-cache-ttl, ignore-cache-for-signing, no-allow-external-cache, allow-emacs-pinentry, no-allow-mark-trusted, disable-scdaemon, and disable-check-own-socket. scdaemon-program is also supported but due to the current implementation, which calls the scdaemon only once, it is not of much use unless you manually kill the scdaemon.

SIGTERM

Shuts down the process but waits until all current requests are fulfilled. If the process has received 3 of these signals and requests are still pending, a shutdown is forced.

SIGINT

Shuts down the process immediately.

SIGUSR1

Dump internal information to the log file.

SIGUSR2

This signal is used for internal purposes.

2.5 Examples

It is important to set the environment variable GPG_TTY in your login shell, for example in the ~/.bashrc init script:

  export GPG_TTY=$(tty)

If you enabled the Ssh Agent Support, you also need to tell ssh about it by adding this to your init script:

unset SSH_AGENT_PID
if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
  export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
fi

2.6 Agent’s Assuan Protocol

Note: this section does only document the protocol, which is used by GnuPG components; it does not deal with the ssh-agent protocol. To see the full specification of each command, use

  gpg-connect-agent 'help COMMAND' /bye

or just ’help’ to list all available commands.

The gpg-agent daemon is started on demand by the GnuPG components.

To identify a key we use a thing called keygrip which is the SHA-1 hash of an canonical encoded S-Expression of the public key as used in Libgcrypt. For the purpose of this interface the keygrip is given as a hex string. The advantage of using this and not the hash of a certificate is that it will be possible to use the same keypair for different protocols, thereby saving space on the token used to keep the secret keys.

The gpg-agent may send status messages during a command or when returning from a command to inform a client about the progress or result of an operation. For example, the INQUIRE_MAXLEN status message may be sent during a server inquire to inform the client of the maximum usable length of the inquired data (which should not be exceeded).

2.6.1 Decrypting a session key

The client asks the server to decrypt a session key. The encrypted session key should have all information needed to select the appropriate secret key or to delegate it to a smartcard.

  SETKEY <keyGrip>

Tell the server about the key to be used for decryption. If this is not used, gpg-agent may try to figure out the key by trying to decrypt the message with each key available.

  PKDECRYPT

The agent checks whether this command is allowed and then does an INQUIRY to get the ciphertext the client should then send the cipher text.

    S: INQUIRE CIPHERTEXT
    C: D (xxxxxx
    C: D xxxx)
    C: END

Please note that the server may send status info lines while reading the data lines from the client. The data send is a SPKI like S-Exp with this structure:

     (enc-val
       (<algo>
         (<param_name1> <mpi>)
 	   ...
         (<param_namen> <mpi>)))

Where algo is a string with the name of the algorithm; see the libgcrypt documentation for a list of valid algorithms. The number and names of the parameters depend on the algorithm. The agent does return an error if there is an inconsistency.

If the decryption was successful the decrypted data is returned by means of "D" lines.

Here is an example session:

   C: PKDECRYPT
   S: INQUIRE CIPHERTEXT
   C: D (enc-val elg (a 349324324)
   C: D    (b 3F444677CA)))
   C: END
   S: # session key follows
   S: S PADDING 0
   S: D (value 1234567890ABCDEF0)
   S: OK descryption successful

The “PADDING” status line is only send if gpg-agent can tell what kind of padding is used. As of now only the value 0 is used to indicate that the padding has been removed.

2.6.2 Signing a Hash

The client ask the agent to sign a given hash value. A default key will be chosen if no key has been set. To set a key a client first uses:

   SIGKEY <keyGrip>

This can be used multiple times to create multiple signature, the list of keys is reset with the next PKSIGN command or a RESET. The server test whether the key is a valid key to sign something and responds with okay.

   SETHASH --hash=<name>|<algo> <hexstring>

The client can use this command to tell the server about the data <hexstring> (which usually is a hash) to be signed. <algo> is the decimal encoded hash algorithm number as used by Libgcrypt. Either <algo> or –hash=<name> must be given. Valid names for <name> are:

sha1

The SHA-1 hash algorithm

sha256

The SHA-256 hash algorithm

rmd160

The RIPE-MD160 hash algorithm

md5

The old and broken MD5 hash algorithm

tls-md5sha1

A combined hash algorithm as used by the TLS protocol.

The actual signing is done using

   PKSIGN <options>

Options are not yet defined, but my later be used to choose among different algorithms. The agent does then some checks, asks for the passphrase and as a result the server returns the signature as an SPKI like S-expression in "D" lines:

     (sig-val
       (<algo>
         (<param_name1> <mpi>)
 	   ...
         (<param_namen> <mpi>)))

The operation is affected by the option

   OPTION use-cache-for-signing=0|1

The default of 1 uses the cache. Setting this option to 0 will lead gpg-agent to ignore the passphrase cache. Note, that there is also a global command line option for gpg-agent to globally disable the caching.

Here is an example session:

   C: SIGKEY <keyGrip>
   S: OK key available
   C: SIGKEY <keyGrip>
   S: OK key available
   C: PKSIGN
   S: # I did ask the user whether he really wants to sign
   S: # I did ask the user for the passphrase
   S: INQUIRE HASHVAL
   C: D ABCDEF012345678901234
   C: END
   S: # signature follows
   S: D (sig-val rsa (s 45435453654612121212))
   S: OK

2.6.3 Generating a Key

This is used to create a new keypair and store the secret key inside the active PSE — which is in most cases a Soft-PSE. A not-yet-defined option allows choosing the storage location. To get the secret key out of the PSE, a special export tool has to be used.

   GENKEY [--no-protection] [--preset] [<cache_nonce>]

Invokes the key generation process and the server will then inquire on the generation parameters, like:

   S: INQUIRE KEYPARM
   C: D (genkey (rsa (nbits  1024)))
   C: END

The format of the key parameters which depends on the algorithm is of the form:

    (genkey
      (algo
        (parameter_name_1 ....)
          ....
        (parameter_name_n ....)))

If everything succeeds, the server returns the *public key* in a SPKI like S-Expression like this:

     (public-key
       (rsa
 	 (n <mpi>)
 	 (e <mpi>)))

Here is an example session:

   C: GENKEY
   S: INQUIRE KEYPARM
   C: D (genkey (rsa (nbits  1024)))
   C: END
   S: D (public-key
   S: D   (rsa (n 326487324683264) (e 10001)))
   S  OK key created

The --no-protection option may be used to prevent prompting for a passphrase to protect the secret key while leaving the secret key unprotected. The --preset option may be used to add the passphrase to the cache using the default cache parameters.

The --inq-passwd option may be used to create the key with a supplied passphrase. When used the agent does an inquiry with the keyword NEWPASSWD to retrieve that passphrase. This option takes precedence over --no-protection; however if the client sends a empty (zero-length) passphrase, this is identical to --no-protection.

2.6.4 Importing a Secret Key

This operation is not yet supported by GpgAgent. Specialized tools are to be used for this.

There is no actual need because we can expect that secret keys created by a 3rd party are stored on a smartcard. If we have generated the key ourself, we do not need to import it.

2.6.5 Export a Secret Key

Not implemented.

Should be done by an extra tool.

2.6.6 Importing a Root Certificate

Actually we do not import a Root Cert but provide a way to validate any piece of data by storing its Hash along with a description and an identifier in the PSE. Here is the interface description:

    ISTRUSTED <fingerprint>

Check whether the OpenPGP primary key or the X.509 certificate with the given fingerprint is an ultimately trusted key or a trusted Root CA certificate. The fingerprint should be given as a hexstring (without any blanks or colons or whatever in between) and may be left padded with 00 in case of an MD5 fingerprint. GPGAgent will answer with:

    OK

The key is in the table of trusted keys.

    ERR 304 (Not Trusted)

The key is not in this table.

Gpg needs the entire list of trusted keys to maintain the web of trust; the following command is therefore quite helpful:

    LISTTRUSTED

GpgAgent returns a list of trusted keys line by line:

    S: D 000000001234454556565656677878AF2F1ECCFF P
    S: D 340387563485634856435645634856438576457A P
    S: D FEDC6532453745367FD83474357495743757435D S
    S: OK

The first item on a line is the hexified fingerprint where MD5 fingerprints are 00 padded to the left and the second item is a flag to indicate the type of key (so that gpg is able to only take care of PGP keys). P = OpenPGP, S = S/MIME. A client should ignore the rest of the line, so that we can extend the format in the future.

Finally a client should be able to mark a key as trusted:

   MARKTRUSTED fingerprint "P"|"S"

The server will then pop up a window to ask the user whether she really trusts this key. For this it will probably ask for a text to be displayed like this:

   S: INQUIRE TRUSTDESC
   C: D Do you trust the key with the fingerprint @FPR@
   C: D bla fasel blurb.
   C: END
   S: OK

Known sequences with the pattern @foo@ are replaced according to this table:

@FPR16@

Format the fingerprint according to gpg rules for a v3 keys.

@FPR20@

Format the fingerprint according to gpg rules for a v4 keys.

@FPR@

Choose an appropriate format to format the fingerprint.

@@

Replaced by a single @

2.6.7 Ask for a passphrase

This function is usually used to ask for a passphrase to be used for symmetric encryption, but may also be used by programs which need special handling of passphrases. This command uses a syntax which helps clients to use the agent with minimum effort.

  GET_PASSPHRASE [--data] [--check] [--no-ask] [--repeat[=N]] \
                 [--qualitybar] cache_id                \
                 [error_message prompt description]

cache_id is expected to be a string used to identify a cached passphrase. Use a X to bypass the cache. With no other arguments the agent returns a cached passphrase or an error. By convention either the hexified fingerprint of the key shall be used for cache_id or an arbitrary string prefixed with the name of the calling application and a colon: Like gpg:somestring.

error_message is either a single X for no error message or a string to be shown as an error message like (e.g. "invalid passphrase"). Blanks must be percent escaped or replaced by +’.

prompt is either a single X for a default prompt or the text to be shown as the prompt. Blanks must be percent escaped or replaced by +.

description is a text shown above the entry field. Blanks must be percent escaped or replaced by +.

The agent either returns with an error or with a OK followed by the hex encoded passphrase. Note that the length of the strings is implicitly limited by the maximum length of a command. If the option --data is used, the passphrase is not returned on the OK line but by regular data lines; this is the preferred method.

If the option --check is used, the standard passphrase constraints checks are applied. A check is not done if the passphrase has been found in the cache.

If the option --no-ask is used and the passphrase is not in the cache the user will not be asked to enter a passphrase but the error code GPG_ERR_NO_DATA is returned.

If the option --qualitybar is used and a minimum passphrase length has been configured, a visual indication of the entered passphrase quality is shown.

  CLEAR_PASSPHRASE cache_id

may be used to invalidate the cache entry for a passphrase. The function returns with OK even when there is no cached passphrase.

2.6.8 Remove a cached passphrase

Use this command to remove a cached passphrase.

  CLEAR_PASSPHRASE [--mode=normal] <cache_id>

The --mode=normal option can be used to clear a cache_id that was set by gpg-agent.

2.6.9 Set a passphrase for a keygrip

This command adds a passphrase to the cache for the specified keygrip.

  PRESET_PASSPHRASE [--inquire] <string_or_keygrip> <timeout> [<hexstring>]

The passphrase is a hexidecimal string when specified. When not specified, the passphrase will be retrieved from the pinentry module unless the --inquire option was specified in which case the passphrase will be retrieved from the client.

The timeout parameter keeps the passphrase cached for the specified number of seconds. A value of -1 means infinate while 0 means the default (currently only a timeout of -1 is allowed, which means to never expire it).

2.6.10 Ask for confirmation

This command may be used to ask for a simple confirmation by presenting a text and 2 buttons: Okay and Cancel.

  GET_CONFIRMATION description

descriptionis displayed along with a Okay and Cancel button. Blanks must be percent escaped or replaced by +. A X may be used to display confirmation dialog with a default text.

The agent either returns with an error or with a OK. Note, that the length of description is implicitly limited by the maximum length of a command.

2.6.11 Check whether a key is available

This can be used to see whether a secret key is available. It does not return any information on whether the key is somehow protected.

  HAVEKEY keygrips

The agent answers either with OK or No_Secret_Key (208). The caller may want to check for other error codes as well. More than one keygrip may be given. In this case the command returns success if at least one of the keygrips corresponds to an available secret key.

2.6.12 Register a smartcard

  LEARN [--send]

This command is used to register a smartcard. With the –send option given the certificates are send back.

2.6.13 Change a Passphrase

  PASSWD [--cache-nonce=<c>] [--passwd-nonce=<s>] [--preset] keygrip

This command is used to interactively change the passphrase of the key identified by the hex string keygrip. The --preset option may be used to add the new passphrase to the cache using the default cache parameters.

2.6.14 Change the standard display

  UPDATESTARTUPTTY

Set the startup TTY and X-DISPLAY variables to the values of this session. This command is useful to direct future pinentry invocations to another screen. It is only required because there is no way in the ssh-agent protocol to convey this information.

2.6.15 Get the Event Counters

  GETEVENTCOUNTER

This function return one status line with the current values of the event counters. The event counters are useful to avoid polling by delaying a poll until something has changed. The values are decimal numbers in the range 0 to UINT_MAX and wrapping around to 0. The actual values should not be relied upon; they shall only be used to detect a change.

The currently defined counters are are:

ANY

Incremented with any change of any of the other counters.

KEY

Incremented for added or removed private keys.

CARD

Incremented for changes of the card readers stati.

2.6.16 Return information about the process

This is a multipurpose function to return a variety of information.

GETINFO what

The value of what specifies the kind of information returned:

version

Return the version of the program.

pid

Return the process id of the process.

socket_name

Return the name of the socket used to connect the agent.

ssh_socket_name

Return the name of the socket used for SSH connections. If SSH support has not been enabled the error GPG_ERR_NO_DATA will be returned.

2.6.17 Set options for the session

Here is a list of session options which are not yet described with other commands. The general syntax for an Assuan option is:

OPTION  key=value

Supported keys are:

agent-awareness

This may be used to tell gpg-agent of which gpg-agent version the client is aware of. gpg-agent uses this information to enable features which might break older clients.

putenv

Change the session’s environment to be used for the Pinentry. Valid values are:

name

Delete envvar name

name=

Set envvar name to the empty string

name=value

Set envvar name to the string value.

use-cache-for-signing

See Assuan command PKSIGN.

allow-pinentry-notify

This does not need any value. It is used to enable the PINENTRY_LAUNCHED inquiry.

pinentry-mode

This option is used to change the operation mode of the pinentry. The following values are defined:

ask

This is the default mode which pops up a pinentry as needed.

cancel

Instead of popping up a pinentry, return the error code GPG_ERR_CANCELED.

error

Instead of popping up a pinentry, return the error code GPG_ERR_NO_PIN_ENTRY.

loopback

Use a loopback pinentry. This fakes a pinentry by using inquiries back to the caller to ask for a passphrase. This option may only be set if the agent has been configured for that. To disable this feature use See option --no-allow-loopback-pinentry.

cache-ttl-opt-preset

This option sets the cache TTL for new entries created by GENKEY and PASSWD commands when using the --preset option. It it is not used a default value is used.

s2k-count

Instead of using the standard S2K count (which is computed on the fly), the given S2K count is used for new keys or when changing the passphrase of a key. Values below 65536 are considered to be 0. This option is valid for the entire session or until reset to 0. This option is useful if the key is later used on boxes which are either much slower or faster than the actual box.

3 Invoking DIRMNGR

Since version 2.1 of GnuPG, dirmngr takes care of accessing the OpenPGP keyservers. As with previous versions it is also used as a server for managing and downloading certificate revocation lists (CRLs) for X.509 certificates, downloading X.509 certificates, and providing access to OCSP providers. Dirmngr is invoked internally by gpg, gpgsm, or via the gpg-connect-agent tool.

See Option Index,for an index to DIRMNGR’s commands and options.

3.1 Commands

Commands are not distinguished from options except for the fact that only one command is allowed.

--version

Print the program version and licensing information. Note that you cannot abbreviate this command.

--help, -h

Print a usage message summarizing the most useful command-line options. Not that you cannot abbreviate this command.

--dump-options

Print a list of all available options and commands. Note that you cannot abbreviate this command.

--server

Run in server mode and wait for commands on the stdin. The default mode is to create a socket and listen for commands there. This is only used for testing.

--daemon

Run in background daemon mode and listen for commands on a socket. Note that this also changes the default home directory and enables the internal certificate validation code. This mode is deprecated.

--list-crls

List the contents of the CRL cache on stdout. This is probably only useful for debugging purposes.

--load-crl file

This command requires a filename as additional argument, and it will make Dirmngr try to import the CRL in file into it’s cache. Note, that this is only possible if Dirmngr is able to retrieve the CA’s certificate directly by its own means. In general it is better to use gpgsm’s --call-dirmngr loadcrl filename command so that gpgsm can help dirmngr.

--fetch-crl url

This command requires an URL as additional argument, and it will make dirmngr try to retrieve an import the CRL from that url into it’s cache. This is mainly useful for debugging purposes. The dirmngr-client provides the same feature for a running dirmngr.

--shutdown

This commands shuts down an running instance of Dirmngr. This command has currently no effect.

--flush

This command removes all CRLs from Dirmngr’s cache. Client requests will thus trigger reading of fresh CRLs.

3.2 Option Summary

--options file

Reads configuration from file instead of from the default per-user configuration file. The default configuration file is named dirmngr.conf and expected in the home directory.

--homedir dir

Set the name of the home directory to dir. This option is only effective when used on the command line. The default depends on the running mode:

With --daemon given on the commandline

the directory named /usr/etc/gnupg is used for configuration files and /usr/var/cache/gnupg for cached CRLs.

Without --daemon given on the commandline

the directory named .gnupg directly below the home directory of the user unless the environment variable GNUPGHOME has been set in which case its value will be used. All kind of data is stored below this directory.

-v

--verbose

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to DIRMNGR, such as -vv.

--log-file file

Append all logging output to file. This is very helpful in seeing what the agent actually does.

--debug-level level

Select the debug level for investigating problems. level may be a numeric value or by a keyword:

none

No debugging at all. A value of less than 1 may be used instead of the keyword.

basic

Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

advanced

More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

expert

Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

guru

All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

--debug flags

This option is only useful for debugging and the behaviour may change at any time without notice. FLAGS are bit encoded and may be given in usual C-Syntax.

--debug-all

Same as --debug=0xffffffff

--gnutls-debug level

Enable debugging of GNUTLS at level.

--debug-wait n

When running in server mode, wait n seconds before entering the actual processing loop and print the pid. This gives time to attach a debugger.

-s

--sh

-c

--csh

Format the info output in daemon mode for use with the standard Bourne shell respective the C-shell . The default ist to guess it based on the environment variable SHELL which is in almost all cases sufficient.

--force

Enabling this option forces loading of expired CRLs; this is only useful for debugging.

--use-tor

This option switches Dirmngr and thus GnuPG into “Tor mode” to route all network access via Tor (an anonymity network). WARNING: As of now this still leaks the DNS queries; e.g. to lookup the hosts in a keyserver pool. Certain other features are disabled if this mode is active.

--keyserver name

Use name as your keyserver. This is the server that gpg communicates with to receive keys, send keys, and search for keys. The format of the name is a URI: ‘scheme:[//]keyservername[:port]’ The scheme is the type of keyserver: "hkp" for the HTTP (or compatible) keyservers, "ldap" for the LDAP keyservers, or "mailto" for the Graff email keyserver. Note that your particular installation of GnuPG may have other keyserver types available as well. Keyserver schemes are case-insensitive. After the keyserver name, optional keyserver configuration options may be provided. These are the same as the --keyserver-options of gpg, but apply only to this particular keyserver.

Most keyservers synchronize with each other, so there is generally no need to send keys to more than one server. The keyserver hkp://keys.gnupg.net uses round robin DNS to give a different keyserver each time you use it.

If exactly two keyservers are configured and only one is a Tor hidden service (.onion), Dirmngr selects the keyserver to use depending on whether Tor is locally running or not. The check for a running Tor is done for each new connection.

--nameserver ipaddr

In “Tor mode” Dirmngr uses a public resolver via Tor to resolve DNS names. If the default public resolver, which is 8.8.8.8, shall not be used a different one can be given using this option. Note that a numerical IP address must be given (IPv6 or IPv4) and that no error checking is done for ipaddr. DNS queries in Tor mode do only work if GnuPG as been build with ADNS support.

--disable-ldap

Entirely disables the use of LDAP.

--disable-http

Entirely disables the use of HTTP.

--ignore-http-dp

When looking for the location of a CRL, the to be tested certificate usually contains so called CRL Distribution Point (DP) entries which are URLs describing the way to access the CRL. The first found DP entry is used. With this option all entries using the HTTP scheme are ignored when looking for a suitable DP.

--ignore-ldap-dp

This is similar to --ignore-http-dp but ignores entries using the LDAP scheme. Both options may be combined resulting in ignoring DPs entirely.

--ignore-ocsp-service-url

Ignore all OCSP URLs contained in the certificate. The effect is to force the use of the default responder.

--honor-http-proxy

If the environment variable http_proxy has been set, use its value to access HTTP servers.

--http-proxy host[:port]

Use host and port to access HTTP servers. The use of this option overrides the environment variable http_proxy regardless whether --honor-http-proxy has been set.

--ldap-proxy host[:port]

Use host and port to connect to LDAP servers. If port is omitted, port 389 (standard LDAP port) is used. This overrides any specified host and port part in a LDAP URL and will also be used if host and port have been omitted from the URL.

--only-ldap-proxy

Never use anything else but the LDAP "proxy" as configured with --ldap-proxy. Usually dirmngr tries to use other configured LDAP server if the connection using the "proxy" failed.

--ldapserverlist-file file

Read the list of LDAP servers to consult for CRLs and certificates from file instead of the default per-user ldap server list file. The default value for file is dirmngr_ldapservers.conf or ldapservers.conf when running in --daemon mode.

This server list file contains one LDAP server per line in the format

HOSTNAME:PORT:USERNAME:PASSWORD:BASE_DN

Lines starting with a ‘#’ are comments.

Note that as usual all strings entered are expected to be UTF-8 encoded. Obviously this will lead to problems if the password has originally been encoded as Latin-1. There is no other solution here than to put such a password in the binary encoding into the file (i.e. non-ascii characters won’t show up readable).¹

--ldaptimeout secs

Specify the number of seconds to wait for an LDAP query before timing out. The default is currently 100 seconds. 0 will never timeout.

--add-servers

This options makes dirmngr add any servers it discovers when validating certificates against CRLs to the internal list of servers to consult for certificates and CRLs.

This options is useful when trying to validate a certificate that has a CRL distribution point that points to a server that is not already listed in the ldapserverlist. Dirmngr will always go to this server and try to download the CRL, but chances are high that the certificate used to sign the CRL is located on the same server. So if dirmngr doesn’t add that new server to list, it will often not be able to verify the signature of the CRL unless the --add-servers option is used.

Note: The current version of dirmngr has this option disabled by default.

--allow-ocsp

This option enables OCSP support if requested by the client.

OCSP requests are rejected by default because they may violate the privacy of the user; for example it is possible to track the time when a user is reading a mail.

--ocsp-responder url

Use url as the default OCSP Responder if the certificate does not contain information about an assigned responder. Note, that --ocsp-signer must also be set to a valid certificate.

--ocsp-signer fpr|file

Use the certificate with the fingerprint fpr to check the responses of the default OCSP Responder. Alternativly a filename can be given in which case the respinse is expected to be signed by one of the certificates described in that file. Any argument which contains a slash, dot or tilde is considered a filename. Usual filename expansion takes place: A tilde at the start followed by a slash is replaced by the content of HOME, no slash at start describes a relative filename which will be searched at the home directory. To make sure that the file is searched in the home directory, either prepend the name with "./" or use a name which contains a dot.

If a response has been signed by a certificate described by these fingerprints no further check upon the validity of this certificate is done.

The format of the FILE is a list of SHA-1 fingerprint, one per line with optional colons between the bytes. Empty lines and lines prefix with a hash mark are ignored.

--ocsp-max-clock-skew n

The number of seconds a skew between the OCSP responder and them local clock is accepted. Default is 600 (20 minutes).

--ocsp-max-period n

Seconds a response is at maximum considered valid after the time given in the thisUpdate field. Default is 7776000 (90 days).

--ocsp-current-period n

The number of seconds an OCSP response is considered valid after the time given in the NEXT_UPDATE datum. Default is 10800 (3 hours).

--max-replies n

Do not return more that n items in one query. The default is 10.

--ignore-cert-extension oid

Add oid to the list of ignored certificate extensions. The oid is expected to be in dotted decimal form, like 2.5.29.3. This option may be used more than once. Critical flagged certificate extensions matching one of the OIDs in the list are treated as if they are actually handled and thus the certificate won’t be rejected due to an unknown critical extension. Use this option with care because extensions are usually flagged as critical for a reason.

--hkp-cacert file

Use the root certificates in file for verification of the TLS certificates used with hkps (keyserver access over TLS). If the file is in PEM format a suffix of .pem is expected for file. This option may be given multiple times to add more root certificates. Tilde expansion is supported.

3.3 Configuration

Dirmngr makes use of several directories when running in daemon mode:

~/.gnupg

This is the standard home directory for all configuration files.

/etc/gnupg/trusted-certs

This directory should be filled with certificates of Root CAs you are trusting in checking the CRLs and signing OCSP Responses.

Usually these are the same certificates you use with the applications making use of dirmngr. It is expected that each of these certificate files contain exactly one DER encoded certificate in a file with the suffix .crt or .der. dirmngr reads those certificates on startup and when given a SIGHUP. Certificates which are not readable or do not make up a proper X.509 certificate are ignored; see the log file for details.

Applications using dirmngr (e.g. gpgsm) can request these certificates to complete a trust chain in the same way as with the extra-certs directory (see below).

Note that for OCSP responses the certificate specified using the option --ocsp-signer is always considered valid to sign OCSP requests.

/etc/gnupg/extra-certs

This directory may contain extra certificates which are preloaded into the interal cache on startup. Applications using dirmngr (e.g. gpgsm) can request cached certificates to complete a trust chain. This is convenient in cases you have a couple intermediate CA certificates or certificates ususally used to sign OCSP responses. These certificates are first tried before going out to the net to look for them. These certificates must also be DER encoded and suffixed with .crt or .der.

~/.gnupg/crls.d

This directory is used to store cached CRLs. The crls.d part will be created by dirmngr if it does not exists but you need to make sure that the upper directory exists.

To be able to see what’s going on you should create the configure file ~/gnupg/dirmngr.conf with at least one line:

log-file ~/dirmngr.log

To be able to perform OCSP requests you probably want to add the line:

allow-ocsp

To make sure that new options are read and that after the installation of a new GnuPG versions the installed dirmngr is running, you may want to kill an existing dirmngr first:

gpgconf --kill dirmngr

You may check the log file to see whether all desired root certificates have been loaded correctly.

3.4 Use of signals.

A running dirmngr may be controlled by signals, i.e. using the kill command to send a signal to the process.

Here is a list of supported signals:

SIGHUP

This signals flushes all internally cached CRLs as well as any cached certificates. Then the certificate cache is reinitialized as on startup. Options are re-read from the configuration file. Instead of sending this signal it is better to use

gpgconf --reload dirmngr

SIGTERM

Shuts down the process but waits until all current requests are fulfilled. If the process has received 3 of these signals and requests are still pending, a shutdown is forced. You may also use

gpgconf --kill dirmngr

instead of this signal

SIGINT

Shuts down the process immediately.

SIGUSR1

This prints some caching statistics to the log file.

3.5 Examples

Here is an example on how to show dirmngr’s internal table of OpenPGP keyserver addresses. The output is intended for debugging purposes and not part of a defined API.

  gpg-connect-agent --dirmngr 'keyserver --hosttable' /bye

To inhibit the use of a particular host you have noticed in one of the keyserver pools, you may use

 gpg-connect-agent --dirmngr 'keyserver --dead pgpkeys.bnd.de' /bye

The description of the keyserver command can be printed using

 gpg-connect-agent --dirmngr 'help keyserver' /bye

3.6 Dirmngr’s Assuan Protocol

Assuan is the IPC protocol used to access dirmngr. This is a description of the commands implemented by dirmngr.

3.6.1 Return the certificate(s) found

Lookup certificate. To allow multiple patterns (which are ORed) quoting is required: Spaces are to be translated into "+" or into "%20"; obviously this requires that the usual escape quoting rules are applied. The server responds with:

  S: D <DER encoded certificate>
  S: END
  S: D <second DER encoded certificate>
  S: END
  S: OK

In this example 2 certificates are returned. The server may return any number of certificates; OK will also be returned when no certificates were found. The dirmngr might return a status line

  S: S TRUNCATED <n>

To indicate that the output was truncated to N items due to a limitation of the server or by an arbitrary set limit.

The option --url may be used if instead of a search pattern a complete URL to the certificate is known:

  C: LOOKUP --url CN%3DWerner%20Koch,o%3DIntevation%20GmbH,c%3DDE?userCertificate

If the option --cache-only is given, no external lookup is done so that only certificates from the cache are returned.

With the option --single, the first and only the first match will be returned. Unless option --cache-only is also used, no local lookup will be done in this case.

3.6.2 Validate a certificate using a CRL or OCSP

  ISVALID [--only-ocsp] [--force-default-responder] certid|certfpr

Check whether the certificate described by the certid has been revoked. Due to caching, the Dirmngr is able to answer immediately in most cases.

The certid is a hex encoded string consisting of two parts, delimited by a single dot. The first part is the SHA-1 hash of the issuer name and the second part the serial number.

Alternatively the certificate’s SHA-1 fingerprint certfpr may be given in which case an OCSP request is done before consulting the CRL. If the option --only-ocsp is given, no fallback to a CRL check will be used. If the option --force-default-responder is given, only the default OCSP responder will be used and any other methods of obtaining an OCSP responder URL won’t be used.

Common return values are:

GPG_ERR_NO_ERROR (0)

This is the positive answer: The certificate is not revoked and we have an up-to-date revocation list for that certificate. If OCSP was used the responder confirmed that the certificate has not been revoked.

GPG_ERR_CERT_REVOKED

This is the negative answer: The certificate has been revoked. Either it is in a CRL and that list is up to date or an OCSP responder informed us that it has been revoked.

GPG_ERR_NO_CRL_KNOWN

No CRL is known for this certificate or the CRL is not valid or out of date.

GPG_ERR_NO_DATA

The OCSP responder returned an “unknown” status. This means that it is not aware of the certificate’s status.

GPG_ERR_NOT_SUPPORTED

This is commonly seen if OCSP support has not been enabled in the configuration.

If DirMngr has not enough information about the given certificate (which is the case for not yet cached certificates), it will will inquire the missing data:

  S: INQUIRE SENDCERT <CertID>
  C: D <DER encoded certificate>
  C: END

A client should be aware that DirMngr may ask for more than one certificate.

If Dirmngr has a certificate but the signature of the certificate could not been validated because the root certificate is not known to dirmngr as trusted, it may ask back to see whether the client trusts this the root certificate:

  S: INQUIRE ISTRUSTED <CertHexfpr>
  C: D 1
  C: END

Only this answer will let Dirmngr consider the CRL as valid.

3.6.3 Validate a certificate using a CRL

Check whether the certificate with FINGERPRINT (SHA-1 hash of the entire X.509 certificate blob) is valid or not by consulting the CRL responsible for this certificate. If the fingerprint has not been given or the certificate is not know, the function inquires the certificate using:

  S: INQUIRE TARGETCERT
  C: D <DER encoded certificate>
  C: END

Thus the caller is expected to return the certificate for the request (which should match FINGERPRINT) as a binary blob. Processing then takes place without further interaction; in particular dirmngr tries to locate other required certificate by its own mechanism which includes a local certificate store as well as a list of trusted root certificates.

The return code is 0 for success; i.e. the certificate has not been revoked or one of the usual error codes from libgpg-error.

3.6.4 Validate a certificate using OCSP

  CHECKOCSP [--force-default-responder] [fingerprint]

Check whether the certificate with fingerprint (the SHA-1 hash of the entire X.509 certificate blob) is valid by consulting the appropiate OCSP responder. If the fingerprint has not been given or the certificate is not known by Dirmngr, the function inquires the certificate using:

  S: INQUIRE TARGETCERT
  C: D <DER encoded certificate>
  C: END

Thus the caller is expected to return the certificate for the request (which should match fingerprint) as a binary blob. Processing then takes place without further interaction; in particular dirmngr tries to locate other required certificates by its own mechanism which includes a local certificate store as well as a list of trusted root certificates.

If the option --force-default-responder is given, only the default OCSP responder is used. This option is the per-command variant of the global option --ignore-ocsp-service-url.

The return code is 0 for success; i.e. the certificate has not been revoked or one of the usual error codes from libgpg-error.

3.6.5 Put a certificate into the internal cache

Put a certificate into the internal cache. This command might be useful if a client knows in advance certificates required for a test and wnats to make sure they get added to the internal cache. It is also helpful for debugging. To get the actual certificate, this command immediately inquires it using

  S: INQUIRE TARGETCERT
  C: D <DER encoded certificate>
  C: END

Thus the caller is expected to return the certificate for the request as a binary blob.

The return code is 0 for success; i.e. the certificate has not been succesfully cached or one of the usual error codes from libgpg-error.

3.6.6 Validate a certificate for debugging

Validate a certificate using the certificate validation function used internally by dirmngr. This command is only useful for debugging. To get the actual certificate, this command immediately inquires it using

  S: INQUIRE TARGETCERT
  C: D <DER encoded certificate>
  C: END

Thus the caller is expected to return the certificate for the request as a binary blob.

4 Invoking GPG

gpg2 is the OpenPGP part of the GNU Privacy Guard (GnuPG). It is a tool to provide digital encryption and signing services using the OpenPGP standard. gpg2 features complete key management and all bells and whistles you can expect from a decent OpenPGP implementation.

In contrast to the standalone command gpg from GnuPG 1.x, which might be better suited for server and embedded platforms, the 2.x version is commonly installed under the name gpg2 and targeted to the desktop as it requires several other modules to be installed.

See Option Index, for an index to gpg2’s commands and options.

Developer information:

4.1 Commands

Commands are not distinguished from options except for the fact that only one command is allowed.

gpg2 may be run with no commands, in which case it will perform a reasonable action depending on the type of file it is given as input (an encrypted message is decrypted, a signature is verified, a file containing keys is listed).

Please remember that option as well as command parsing stops as soon as a non-option is encountered, you can explicitly stop parsing by using the special option --.

4.1.1 Commands not specific to the function

--version

Print the program version and licensing information. Note that you cannot abbreviate this command.

--help

-h

Print a usage message summarizing the most useful command line options. Note that you cannot abbreviate this command.

--warranty

Print warranty information.

--dump-options

Print a list of all available options and commands. Note that you cannot abbreviate this command.

4.1.2 Commands to select the type of operation

--sign

-s

Make a signature. This command may be combined with --encrypt (for a signed and encrypted message), --symmetric (for a signed and symmetrically encrypted message), or --encrypt and --symmetric together (for a signed message that may be decrypted via a secret key or a passphrase). The key to be used for signing is chosen by default or can be set with the --local-user and --default-key options.

--clearsign

Make a clear text signature. The content in a clear text signature is readable without any special software. OpenPGP software is only needed to verify the signature. Clear text signatures may modify end-of-line whitespace for platform independence and are not intended to be reversible. The key to be used for signing is chosen by default or can be set with the --local-user and --default-key options.

--detach-sign

-b

Make a detached signature.

--encrypt

-e

Encrypt data. This option may be combined with --sign (for a signed and encrypted message), --symmetric (for a message that may be decrypted via a secret key or a passphrase), or --sign and --symmetric together (for a signed message that may be decrypted via a secret key or a passphrase).

--symmetric

-c

Encrypt with a symmetric cipher using a passphrase. The default symmetric cipher used is AES-128, but may be chosen with the --cipher-algo option. This option may be combined with --sign (for a signed and symmetrically encrypted message), --encrypt (for a message that may be decrypted via a secret key or a passphrase), or --sign and --encrypt together (for a signed message that may be decrypted via a secret key or a passphrase).

--store

Store only (make a simple literal data packet).

--decrypt

-d

Decrypt the file given on the command line (or STDIN if no file is specified) and write it to STDOUT (or the file specified with --output). If the decrypted file is signed, the signature is also verified. This command differs from the default operation, as it never writes to the filename which is included in the file and it rejects files which don’t begin with an encrypted message.

--verify

Assume that the first argument is a signed file and verify it without generating any output. With no arguments, the signature packet is read from STDIN. If only a one argument is given, it is expected to be a complete signature.

With more than 1 argument, the first should be a detached signature and the remaining files make up the the signed data. To read the signed data from STDIN, use ‘-’ as the second filename. For security reasons a detached signature cannot read the signed material from STDIN without denoting it in the above way.

Note: If the option --batch is not used, gpg2 may assume that a single argument is a file with a detached signature and it will try to find a matching data file by stripping certain suffixes. Using this historical feature to verify a detached signature is strongly discouraged; always specify the data file too.

Note: When verifying a cleartext signature, gpg verifies only what makes up the cleartext signed data and not any extra data outside of the cleartext signature or header lines following directly the dash marker line. The option --output may be used to write out the actual signed data; but there are other pitfalls with this format as well. It is suggested to avoid cleartext signatures in favor of detached signatures.

--multifile

This modifies certain other commands to accept multiple files for processing on the command line or read from STDIN with each filename on a separate line. This allows for many files to be processed at once. --multifile may currently be used along with --verify, --encrypt, and --decrypt. Note that --multifile --verify may not be used with detached signatures.

--verify-files

Identical to --multifile --verify.

--encrypt-files

Identical to --multifile --encrypt.

--decrypt-files

Identical to --multifile --decrypt.

--list-keys

-k

--list-public-keys

List all keys from the public keyrings, or just the keys given on the command line.

Avoid using the output of this command in scripts or other programs as it is likely to change as GnuPG changes. See --with-colons for a machine-parseable key listing command that is appropriate for use in scripts and other programs. Never use the regular output for scripts - it is only for human consumption.

--list-secret-keys

-K

List all keys from the secret keyrings, or just the ones given on the command line. A # after the letters sec means that the secret key is not usable (for example, if it was created via --export-secret-subkeys). See also --list-keys.

--list-sigs

Same as --list-keys, but the signatures are listed too. This command has the same effect as using --list-keys with --with-sig-list.

For each signature listed, there are several flags in between the "sig" tag and keyid. These flags give additional information about each signature. From left to right, they are the numbers 1-3 for certificate check level (see --ask-cert-level), "L" for a local or non-exportable signature (see --lsign-key), "R" for a nonRevocable signature (see the --edit-key command "nrsign"), "P" for a signature that contains a policy URL (see --cert-policy-url), "N" for a signature that contains a notation (see --cert-notation), "X" for an eXpired signature (see --ask-cert-expire), and the numbers 1-9 or "T" for 10 and above to indicate trust signature levels (see the --edit-key command "tsign").

--check-sigs

Same as --list-sigs, but the signatures are verified. Note that for performance reasons the revocation status of a signing key is not shown. This command has the same effect as using --list-keys with --with-sig-check.

The status of the verification is indicated by a flag directly following the "sig" tag (and thus before the flags described above for --list-sigs). A "!" indicates that the signature has been successfully verified, a "-" denotes a bad signature and a "%" is used if an error occurred while checking the signature (e.g. a non supported algorithm).

--locate-keys

Locate the keys given as arguments. This command basically uses the same algorithm as used when locating keys for encryption or signing and may thus be used to see what keys gpg2 might use. In particular external methods as defined by --auto-key-locate may be used to locate a key. Only public keys are listed.

--fingerprint

List all keys (or the specified ones) along with their fingerprints. This is the same output as --list-keys but with the additional output of a line with the fingerprint. May also be combined with --list-sigs or --check-sigs. If this command is given twice, the fingerprints of all secondary keys are listed too. This command also forces pretty printing of fingerprints if the keyid format has been set to "none".

--list-packets

List only the sequence of packets. This command is only useful for debugging. When used with option --verbose the actual MPI values are dumped and not only their lengths. Note that the output of this command may change with new releases.

--card-edit

Present a menu to work with a smartcard. The subcommand "help" provides an overview on available commands. For a detailed description, please see the Card HOWTO at https://gnupg.org/documentation/howtos.html#GnuPG-cardHOWTO .

--card-status

Show the content of the smart card.

--change-pin

Present a menu to allow changing the PIN of a smartcard. This functionality is also available as the subcommand "passwd" with the --card-edit command.

--delete-keys name

--delete-keys name

Remove key from the public keyring. In batch mode either --yes is required or the key must be specified by fingerprint. This is a safeguard against accidental deletion of multiple keys.

--delete-secret-keys name

gRemove key from the secret keyring. In batch mode the key must be specified by fingerprint. The option --yes can be used to advice gpg-agent not to request a confirmation. This extra pre-caution is done because gpg can’t be sure that the secret key (as controlled by gpg-agent) is only used for the given OpenPGP public key.

--delete-secret-and-public-key name

Same as --delete-key, but if a secret key exists, it will be removed first. In batch mode the key must be specified by fingerprint. The option --yes can be used to advice gpg-agent not to request a confirmation.

--export

Either export all keys from all keyrings (default keyrings and those registered via option --keyring), or if at least one name is given, those of the given name. The exported keys are written to STDOUT or to the file given with option --output. Use together with --armor to mail those keys.

--send-keys key IDs

Similar to --export but sends the keys to a keyserver. Fingerprints may be used instead of key IDs. Option --keyserver must be used to give the name of this keyserver. Don’t send your complete keyring to a keyserver — select only those keys which are new or changed by you. If no key IDs are given, gpg does nothing.

--export-secret-keys

--export-secret-subkeys

Same as --export, but exports the secret keys instead. The exported keys are written to STDOUT or to the file given with option --output. This command is often used along with the option --armor to allow easy printing of the key for paper backup; however the external tool paperkey does a better job for creating backups on paper. Note that exporting a secret key can be a security risk if the exported keys are send over an insecure channel.

The second form of the command has the special property to render the secret part of the primary key useless; this is a GNU extension to OpenPGP and other implementations can not be expected to successfully import such a key. Its intended use is to generated a full key with an additional signing subkey on a dedicated machine and then using this command to export the key without the primary key to the main machine.

GnuPG may ask you to enter the passphrase for the key. This is required because the internal protection method of the secret key is different from the one specified by the OpenPGP protocol.

--export-ssh-key

This command is used to export a key in the OpenSSH public key format. It requires the specification of one key by the usual means and exports the latest valid subkey which has an authentication capability to STDOUT or to the file given with option --output. That output can directly be added to ssh’s authorized_key file.

By specifying the key to export using a key ID or a fingerprint suffixed with an exclamation mark (!), a specific subkey or the primary key can be exported. This does not even require that the key has the authentication capability flag set.

--import

--fast-import

Import/merge keys. This adds the given keys to the keyring. The fast version is currently just a synonym.

There are a few other options which control how this command works. Most notable here is the --import-options merge-only option which does not insert new keys but does only the merging of new signatures, user-IDs and subkeys.

--recv-keys key IDs

Import the keys with the given key IDs from a keyserver. Option --keyserver must be used to give the name of this keyserver.

--refresh-keys

Request updates from a keyserver for keys that already exist on the local keyring. This is useful for updating a key with the latest signatures, user IDs, etc. Calling this with no arguments will refresh the entire keyring. Option --keyserver must be used to give the name of the keyserver for all keys that do not have preferred keyservers set (see --keyserver-options honor-keyserver-url).

--search-keys names

Search the keyserver for the given names. Multiple names given here will be joined together to create the search string for the keyserver. Option --keyserver must be used to give the name of this keyserver. Keyservers that support different search methods allow using the syntax specified in "How to specify a user ID" below. Note that different keyserver types support different search methods. Currently only LDAP supports them all.

--fetch-keys URIs

Retrieve keys located at the specified URIs. Note that different installations of GnuPG may support different protocols (HTTP, FTP, LDAP, etc.). When using HTTPS the system provided root certificates are used by this command.

--update-trustdb

Do trust database maintenance. This command iterates over all keys and builds the Web of Trust. This is an interactive command because it may have to ask for the "ownertrust" values for keys. The user has to give an estimation of how far she trusts the owner of the displayed key to correctly certify (sign) other keys. GnuPG only asks for the ownertrust value if it has not yet been assigned to a key. Using the --edit-key menu, the assigned value can be changed at any time.

--check-trustdb

Do trust database maintenance without user interaction. From time to time the trust database must be updated so that expired keys or signatures and the resulting changes in the Web of Trust can be tracked. Normally, GnuPG will calculate when this is required and do it automatically unless --no-auto-check-trustdb is set. This command can be used to force a trust database check at any time. The processing is identical to that of --update-trustdb but it skips keys with a not yet defined "ownertrust".

For use with cron jobs, this command can be used together with --batch in which case the trust database check is done only if a check is needed. To force a run even in batch mode add the option --yes.

--export-ownertrust

Send the ownertrust values to STDOUT. This is useful for backup purposes as these values are the only ones which can’t be re-created from a corrupted trustdb. Example:

  gpg2 --export-ownertrust > otrust.txt

--import-ownertrust

Update the trustdb with the ownertrust values stored in files (or STDIN if not given); existing values will be overwritten. In case of a severely damaged trustdb and if you have a recent backup of the ownertrust values (e.g. in the file otrust.txt, you may re-create the trustdb using these commands:

  cd ~/.gnupg
  rm trustdb.gpg
  gpg2 --import-ownertrust < otrust.txt

--rebuild-keydb-caches

When updating from version 1.0.6 to 1.0.7 this command should be used to create signature caches in the keyring. It might be handy in other situations too.

--print-md algo

--print-mds

Print message digest of algorithm ALGO for all given files or STDIN. With the second form (or a deprecated "*" as algo) digests for all available algorithms are printed.

--gen-random 0|1|2 count

Emit count random bytes of the given quality level 0, 1 or 2. If count is not given or zero, an endless sequence of random bytes will be emitted. If used with --armor the output will be base64 encoded. PLEASE, don’t use this command unless you know what you are doing; it may remove precious entropy from the system!

--gen-prime mode bits

Use the source, Luke :-). The output format is still subject to change.

--enarmor

--dearmor

Pack or unpack an arbitrary input into/from an OpenPGP ASCII armor. This is a GnuPG extension to OpenPGP and in general not very useful.

--tofu-policy auto|good|unknown|bad|ask key...

Set the TOFU policy for all the bindings associated with the specified keys. For more information about the meaning of the policies, see trust-model-tofu. The keys may be specified either by their fingerprint (preferred) or their keyid.

4.1.3 How to manage your keys

This section explains the main commands for key management

--quick-gen-key user-id [algo [usage [expire]]]

This is a simple command to generate a standard key with one user id. In contrast to --gen-key the key is generated directly without the need to answer a bunch of prompts. Unless the option --yes is given, the key creation will be canceled if the given user id already exists in the key ring.

If invoked directly on the console without any special options an answer to a “Continue?” style confirmation prompt is required. In case the user id already exists in the key ring a second prompt to force the creation of the key will show up.

If any of the optional arguments are given, only the primary key is created and no prompts are shown. For a description of these optional arguments see the command --quick-addkey. The usage accepts also the value “cert” which can be used to create a certification only primary key; the default is to a create certification and signing key.

If this command is used with --batch, --pinentry-mode has been set to loopback, and one of the passphrase options (--passphrase, --passphrase-fd, or passphrase-file) is used, the supplied passphrase is used for the new key and the agent does not ask for it. To create a key without any protection --passphrase '' may be used.

--quick-addkey fpr [algo [usage [expire]]]

Directly add a subkey to the key identified by the fingerprint fpr. Without the optional arguments an encryption subkey is added. If any of the arguments are given a more specific subkey is added.

algo may be any of the supported algorithms or curve names given in the format as used by key listings. To use the default algorithm the string “default” or “-” can be used. Supported algorithms are “rsa”, “dsa”, “elg”, “ed25519”, “cv25519”, and other ECC curves. For example the string “rsa” adds an RSA key with the default key length; a string “rsa4096” requests that the key length is 4096 bits.

Depending on the given algo the subkey may either be an encryption subkey or a signing subkey. If an algorithm is capable of signing and encryption and such a subkey is desired, a usage string must be given. This string is either “default” or “-” to keep the default or a comma delimited list of keywords: “sign” for a signing subkey, “auth” for an authentication subkey, and “encr” for an encryption subkey (“encrypt” can be used as alias for “encr”). The valid combinations depend on the algorithm.

The expire argument can be used to specify an expiration date for the subkey. Several formats are supported; commonly the ISO YYYY-MM-DD format is used. The values “never”, “none”, or “-” can be used for no expiration date.

--gen-key

Generate a new key pair using the current default parameters. This is the standard command to create a new key. In addition to the key a revocation certificate is created and stored in the openpgp-revocs.d directory below the GnuPG home directory.

--full-gen-key

Generate a new key pair with dialogs for all options. This is an extended version of --gen-key.

There is also a feature which allows you to create keys in batch mode. See the manual section “Unattended key generation” on how to use this.

--gen-revoke name

Generate a revocation certificate for the complete key. To only revoke a subkey or a key signature, use the --edit command.

This command merely creates the revocation certificate so that it can be used to revoke the key if that is ever needed. To actually revoke a key the created revocation certificate needs to be merged with the key to revoke. This is done by importing the revocation certificate using the --import command. Then the revoked key needs to be published, which is best done by sending the key to a keyserver (command --send-key) and by exporting (--export) it to a file which is then send to frequent communication partners.

--desig-revoke name

Generate a designated revocation certificate for a key. This allows a user (with the permission of the keyholder) to revoke someone else’s key.

--edit-key

Present a menu which enables you to do most of the key management related tasks. It expects the specification of a key on the command line.

uid n

Toggle selection of user ID or photographic user ID with index n. Use * to select all and 0 to deselect all.

key n

Toggle selection of subkey with index n or key ID n. Use * to select all and 0 to deselect all.

sign

Make a signature on key of user name If the key is not yet signed by the default user (or the users given with -u), the program displays the information of the key again, together with its fingerprint and asks whether it should be signed. This question is repeated for all users specified with -u.

lsign

Same as "sign" but the signature is marked as non-exportable and will therefore never be used by others. This may be used to make keys valid only in the local environment.

nrsign

Same as "sign" but the signature is marked as non-revocable and can therefore never be revoked.

tsign

Make a trust signature. This is a signature that combines the notions of certification (like a regular signature), and trust (like the "trust" command). It is generally only useful in distinct communities or groups. For more information please read the sections “Trust Signature” and “Regular Expression” in RFC-4880.

Note that "l" (for local / non-exportable), "nr" (for non-revocable, and "t" (for trust) may be freely mixed and prefixed to "sign" to create a signature of any type desired.

If the option --only-sign-text-ids is specified, then any non-text based user ids (e.g., photo IDs) will not be selected for signing.

delsig

Delete a signature. Note that it is not possible to retract a signature, once it has been send to the public (i.e. to a keyserver). In that case you better use revsig.

revsig

Revoke a signature. For every signature which has been generated by one of the secret keys, GnuPG asks whether a revocation certificate should be generated.

check

Check the signatures on all selected user IDs. With the extra option selfsig only self-signatures are shown.

adduid

Create an additional user ID.

addphoto

Create a photographic user ID. This will prompt for a JPEG file that will be embedded into the user ID. Note that a very large JPEG will make for a very large key. Also note that some programs will display your JPEG unchanged (GnuPG), and some programs will scale it to fit in a dialog box (PGP).

showphoto

Display the selected photographic user ID.

deluid

Delete a user ID or photographic user ID. Note that it is not possible to retract a user id, once it has been send to the public (i.e. to a keyserver). In that case you better use revuid.

revuid

Revoke a user ID or photographic user ID.

primary

Flag the current user id as the primary one, removes the primary user id flag from all other user ids and sets the timestamp of all affected self-signatures one second ahead. Note that setting a photo user ID as primary makes it primary over other photo user IDs, and setting a regular user ID as primary makes it primary over other regular user IDs.

keyserver

Set a preferred keyserver for the specified user ID(s). This allows other users to know where you prefer they get your key from. See --keyserver-options honor-keyserver-url for more on how this works. Setting a value of "none" removes an existing preferred keyserver.

notation

Set a name=value notation for the specified user ID(s). See --cert-notation for more on how this works. Setting a value of "none" removes all notations, setting a notation prefixed with a minus sign (-) removes that notation, and setting a notation name (without the =value) prefixed with a minus sign removes all notations with that name.

pref

List preferences from the selected user ID. This shows the actual preferences, without including any implied preferences.

showpref

More verbose preferences listing for the selected user ID. This shows the preferences in effect by including the implied preferences of 3DES (cipher), SHA-1 (digest), and Uncompressed (compression) if they are not already included in the preference list. In addition, the preferred keyserver and signature notations (if any) are shown.

setpref string

Set the list of user ID preferences to string for all (or just the selected) user IDs. Calling setpref with no arguments sets the preference list to the default (either built-in or set via --default-preference-list), and calling setpref with "none" as the argument sets an empty preference list. Use gpg2 --version to get a list of available algorithms. Note that while you can change the preferences on an attribute user ID (aka "photo ID"), GnuPG does not select keys via attribute user IDs so these preferences will not be used by GnuPG.

When setting preferences, you should list the algorithms in the order which you’d like to see them used by someone else when encrypting a message to your key. If you don’t include 3DES, it will be automatically added at the end. Note that there are many factors that go into choosing an algorithm (for example, your key may not be the only recipient), and so the remote OpenPGP application being used to send to you may or may not follow your exact chosen order for a given message. It will, however, only choose an algorithm that is present on the preference list of every recipient key. See also the INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS section below.

addkey

Add a subkey to this key.

addcardkey

Generate a subkey on a card and add it to this key.

keytocard

Transfer the selected secret subkey (or the primary key if no subkey has been selected) to a smartcard. The secret key in the keyring will be replaced by a stub if the key could be stored successfully on the card and you use the save command later. Only certain key types may be transferred to the card. A sub menu allows you to select on what card to store the key. Note that it is not possible to get that key back from the card - if the card gets broken your secret key will be lost unless you have a backup somewhere.

bkuptocard file

Restore the given file to a card. This command may be used to restore a backup key (as generated during card initialization) to a new card. In almost all cases this will be the encryption key. You should use this command only with the corresponding public key and make sure that the file given as argument is indeed the backup to restore. You should then select 2 to restore as encryption key. You will first be asked to enter the passphrase of the backup key and then for the Admin PIN of the card.

delkey

Remove a subkey (secondary key). Note that it is not possible to retract a subkey, once it has been send to the public (i.e. to a keyserver). In that case you better use revkey.

revkey

Revoke a subkey.

expire

Change the key or subkey expiration time. If a subkey is selected, the expiration time of this subkey will be changed. With no selection, the key expiration of the primary key is changed.

trust

Change the owner trust value for the key. This updates the trust-db immediately and no save is required.

disable

enable

Disable or enable an entire key. A disabled key can not normally be used for encryption.

addrevoker

Add a designated revoker to the key. This takes one optional argument: "sensitive". If a designated revoker is marked as sensitive, it will not be exported by default (see export-options).

passwd

Change the passphrase of the secret key.

toggle

This is dummy command which exists only for backward compatibility.

clean

Compact (by removing all signatures except the selfsig) any user ID that is no longer usable (e.g. revoked, or expired). Then, remove any signatures that are not usable by the trust calculations. Specifically, this removes any signature that does not validate, any signature that is superseded by a later signature, revoked signatures, and signatures issued by keys that are not present on the keyring.

minimize

Make the key as small as possible. This removes all signatures from each user ID except for the most recent self-signature.

cross-certify

Add cross-certification signatures to signing subkeys that may not currently have them. Cross-certification signatures protect against a subtle attack against signing subkeys. See --require-cross-certification. All new keys generated have this signature by default, so this option is only useful to bring older keys up to date.

save

Save all changes to the key rings and quit.

quit

Quit the program without updating the key rings.

The listing shows you the key with its secondary keys and all user ids. The primary user id is indicated by a dot, and selected keys or user ids are indicated by an asterisk. The trust value is displayed with the primary key: the first is the assigned owner trust and the second is the calculated trust value. Letters are used for the values:

-

No ownertrust assigned / not yet calculated.

e

Trust calculation has failed; probably due to an expired key.

q

Not enough information for calculation.

n

Never trust this key.

m

Marginally trusted.

f

Fully trusted.

u

Ultimately trusted.

--sign-key name

Signs a public key with your secret key. This is a shortcut version of the subcommand "sign" from --edit.

--lsign-key name

Signs a public key with your secret key but marks it as non-exportable. This is a shortcut version of the subcommand "lsign" from --edit-key.

--quick-sign-key fpr [names]

--quick-lsign-key fpr [names]

Directly sign a key from the passphrase without any further user interaction. The fpr must be the verified primary fingerprint of a key in the local keyring. If no names are given, all useful user ids are signed; with given [names] only useful user ids matching one of theses names are signed. By default, or if a name is prefixed with a ’*’, a case insensitive substring match is used. If a name is prefixed with a ’=’ a case sensitive exact match is done.

The command --quick-lsign-key marks the signatures as non-exportable. If such a non-exportable signature already exists the --quick-sign-key turns it into a exportable signature.

This command uses reasonable defaults and thus does not provide the full flexibility of the "sign" subcommand from --edit-key. Its intended use is to help unattended key signing by utilizing a list of verified fingerprints.

--quick-adduid user-id new-user-id

This command adds a new user id to an existing key. In contrast to the interactive sub-command adduid of --edit-key the new-user-id is added verbatim with only leading and trailing white space removed, it is expected to be UTF-8 encoded, and no checks on its form are applied.

--quick-revuid user-id user-id-to-revoke

This command revokes a User ID on an existing key. It cannot be used to revoke the last User ID on key (some non-revoked User ID must remain), with revocation reason “User ID is no longer valid”. If you want to specify a different revocation reason, or to supply supplementary revocation text, you should use the interactive sub-command revuid of --edit-key.

--passwd user_id

Change the passphrase of the secret key belonging to the certificate specified as user_id. This is a shortcut for the sub-command passwd of the edit key menu.

4.2 Option Summary

gpg2 features a bunch of options to control the exact behaviour and to change the default configuration.

Long options can be put in an options file (default "~/.gnupg/gpg.conf"). Short option names will not work - for example, "armor" is a valid option for the options file, while "a" is not. Do not write the 2 dashes, but simply the name of the option and any required arguments. Lines with a hash (’#’) as the first non-white-space character are ignored. Commands may be put in this file too, but that is not generally useful as the command will execute automatically with every execution of gpg.

Please remember that option parsing stops as soon as a non-option is encountered, you can explicitly stop parsing by using the special option --.

4.2.1 How to change the configuration

These options are used to change the configuration and are usually found in the option file.

--default-key name

Use name as the default key to sign with. If this option is not used, the default key is the first key found in the secret keyring. Note that -u or --local-user overrides this option. This option may be given multiple times. In this case, the last key for which a secret key is available is used. If there is no secret key available for any of the specified values, GnuPG will not emit an error message but continue as if this option wasn’t given.

--default-recipient name

Use name as default recipient if option --recipient is not used and don’t ask if this is a valid one. name must be non-empty.

--default-recipient-self

Use the default key as default recipient if option --recipient is not used and don’t ask if this is a valid one. The default key is the first one from the secret keyring or the one set with --default-key.

--no-default-recipient

Reset --default-recipient and --default-recipient-self.

-v, --verbose

Give more information during processing. If used twice, the input data is listed in detail.

--no-verbose

Reset verbose level to 0.

-q, --quiet

Try to be as quiet as possible.

--batch

--no-batch

Use batch mode. Never ask, do not allow interactive commands. --no-batch disables this option. Note that even with a filename given on the command line, gpg might still need to read from STDIN (in particular if gpg figures that the input is a detached signature and no data file has been specified). Thus if you do not want to feed data via STDIN, you should connect STDIN to /dev/null.

--no-tty

Make sure that the TTY (terminal) is never used for any output. This option is needed in some cases because GnuPG sometimes prints warnings to the TTY even if --batch is used.

--yes

Assume "yes" on most questions.

--no

Assume "no" on most questions.

--list-options parameters

This is a space or comma delimited string that gives options used when listing keys and signatures (that is, --list-keys, --list-sigs, --list-public-keys, --list-secret-keys, and the --edit-key functions). Options can be prepended with a no- (after the two dashes) to give the opposite meaning. The options are:

show-photos

Causes --list-keys, --list-sigs, --list-public-keys, and --list-secret-keys to display any photo IDs attached to the key. Defaults to no. See also --photo-viewer. Does not work with --with-colons: see --attribute-fd for the appropriate way to get photo data for scripts and other frontends.

show-usage

Show usage information for keys and subkeys in the standard key listing. This is a list of letters indicating the allowed usage for a key (E=encryption, S=signing, C=certification, A=authentication). Defaults to yes.

show-policy-urls

Show policy URLs in the --list-sigs or --check-sigs listings. Defaults to no.

show-notations

show-std-notations

show-user-notations

Show all, IETF standard, or user-defined signature notations in the --list-sigs or --check-sigs listings. Defaults to no.

show-keyserver-urls

Show any preferred keyserver URL in the --list-sigs or --check-sigs listings. Defaults to no.

show-uid-validity

Display the calculated validity of user IDs during key listings. Defaults to yes.

show-unusable-uids

Show revoked and expired user IDs in key listings. Defaults to no.

show-unusable-subkeys

Show revoked and expired subkeys in key listings. Defaults to no.

show-keyring

Display the keyring name at the head of key listings to show which keyring a given key resides on. Defaults to no.

show-sig-expire

Show signature expiration dates (if any) during --list-sigs or --check-sigs listings. Defaults to no.

show-sig-subpackets

Include signature subpackets in the key listing. This option can take an optional argument list of the subpackets to list. If no argument is passed, list all subpackets. Defaults to no. This option is only meaningful when using --with-colons along with --list-sigs or --check-sigs.

--verify-options parameters

This is a space or comma delimited string that gives options used when verifying signatures. Options can be prepended with a ‘no-’ to give the opposite meaning. The options are:

show-photos

Display any photo IDs present on the key that issued the signature. Defaults to no. See also --photo-viewer.

show-policy-urls

Show policy URLs in the signature being verified. Defaults to yes.

show-notations

show-std-notations

show-user-notations

Show all, IETF standard, or user-defined signature notations in the signature being verified. Defaults to IETF standard.

show-keyserver-urls

Show any preferred keyserver URL in the signature being verified. Defaults to yes.

show-uid-validity

Display the calculated validity of the user IDs on the key that issued the signature. Defaults to yes.

show-unusable-uids

Show revoked and expired user IDs during signature verification. Defaults to no.

show-primary-uid-only

Show only the primary user ID during signature verification. That is all the AKA lines as well as photo Ids are not shown with the signature verification status.

pka-lookups

Enable PKA lookups to verify sender addresses. Note that PKA is based on DNS, and so enabling this option may disclose information on when and what signatures are verified or to whom data is encrypted. This is similar to the "web bug" described for the --auto-key-retrieve option.

pka-trust-increase

Raise the trust in a signature to full if the signature passes PKA validation. This option is only meaningful if pka-lookups is set.

--enable-large-rsa

--disable-large-rsa

With –gen-key and –batch, enable the creation of RSA secret keys as large as 8192 bit. Note: 8192 bit is more than is generally recommended. These large keys don’t significantly improve security, but they are more expensive to use, and their signatures and certifications are larger. This option is only available if the binary was build with large-secmem support.

--enable-dsa2

--disable-dsa2

Enable hash truncation for all DSA keys even for old DSA Keys up to 1024 bit. This is also the default with --openpgp. Note that older versions of GnuPG also required this flag to allow the generation of DSA larger than 1024 bit.

--photo-viewer string

This is the command line that should be run to view a photo ID. "%i" will be expanded to a filename containing the photo. "%I" does the same, except the file will not be deleted once the viewer exits. Other flags are "%k" for the key ID, "%K" for the long key ID, "%f" for the key fingerprint, "%t" for the extension of the image type (e.g. "jpg"), "%T" for the MIME type of the image (e.g. "image/jpeg"), "%v" for the single-character calculated validity of the image being viewed (e.g. "f"), "%V" for the calculated validity as a string (e.g. "full"), "%U" for a base32 encoded hash of the user ID, and "%%" for an actual percent sign. If neither %i or %I are present, then the photo will be supplied to the viewer on standard input.

The default viewer is "xloadimage -fork -quiet -title ’KeyID 0x%k’ STDIN". Note that if your image viewer program is not secure, then executing it from GnuPG does not make it secure.

--exec-path string

Sets a list of directories to search for photo viewers and keyserver helpers. If not provided, keyserver helpers use the compiled-in default directory, and photo viewers use the PATH environment variable. Note, that on W32 system this value is ignored when searching for keyserver helpers.

--keyring file

Add file to the current list of keyrings. If file begins with a tilde and a slash, these are replaced by the $HOME directory. If the filename does not contain a slash, it is assumed to be in the GnuPG home directory ("~/.gnupg" if --homedir or $GNUPGHOME is not used).

Note that this adds a keyring to the current list. If the intent is to use the specified keyring alone, use --keyring along with --no-default-keyring.

If the the option --no-keyring has been used no keyrings will be used at all.

--secret-keyring file

This is an obsolete option and ignored. All secret keys are stored in the private-keys-v1.d directory below the GnuPG home directory.

--primary-keyring file

Designate file as the primary public keyring. This means that newly imported keys (via --import or keyserver --recv-from) will go to this keyring.

--trustdb-name file

Use file instead of the default trustdb. If file begins with a tilde and a slash, these are replaced by the $HOME directory. If the filename does not contain a slash, it is assumed to be in the GnuPG home directory (~/.gnupg if --homedir or $GNUPGHOME is not used).

--homedir dir

Set the name of the home directory to dir. If this option is not used, the home directory defaults to ~/.gnupg. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable GNUPGHOME or (on Windows systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

On Windows systems it is possible to install GnuPG as a portable application. In this case only this command line option is considered, all other ways to set a home directory are ignored.

To install GnuPG as a portable application under Windows, create an empty file name gpgconf.ctl in the same directory as the tool gpgconf.exe. The root of the installation is than that directory; or, if gpgconf.exe has been installed directly below a directory named bin, its parent directory. You also need to make sure that the following directories exist and are writable: ROOT/home for the GnuPG home and ROOT/usr/var/cache/gnupg for internal cache files.

--display-charset name

Set the name of the native character set. This is used to convert some informational strings like user IDs to the proper UTF-8 encoding. Note that this has nothing to do with the character set of data to be encrypted or signed; GnuPG does not recode user-supplied data. If this option is not used, the default character set is determined from the current locale. A verbosity level of 3 shows the chosen set. Valid values for name are:

iso-8859-1

This is the Latin 1 set.

iso-8859-2

The Latin 2 set.

iso-8859-15

This is currently an alias for the Latin 1 set.

koi8-r

The usual Russian set (rfc1489).

utf-8

Bypass all translations and assume that the OS uses native UTF-8 encoding.

--utf8-strings

--no-utf8-strings

Assume that command line arguments are given as UTF8 strings. The default (--no-utf8-strings) is to assume that arguments are encoded in the character set as specified by --display-charset. These options affect all following arguments. Both options may be used multiple times.

--options file

Read options from file and do not try to read them from the default options file in the homedir (see --homedir). This option is ignored if used in an options file.

--no-options

Shortcut for --options /dev/null. This option is detected before an attempt to open an option file. Using this option will also prevent the creation of a ~/.gnupg homedir.

-z n

--compress-level n

--bzip2-compress-level n

Set compression level to n for the ZIP and ZLIB compression algorithms. The default is to use the default compression level of zlib (normally 6). --bzip2-compress-level sets the compression level for the BZIP2 compression algorithm (defaulting to 6 as well). This is a different option from --compress-level since BZIP2 uses a significant amount of memory for each additional compression level. -z sets both. A value of 0 for n disables compression.

--bzip2-decompress-lowmem

Use a different decompression method for BZIP2 compressed files. This alternate method uses a bit more than half the memory, but also runs at half the speed. This is useful under extreme low memory circumstances when the file was originally compressed at a high --bzip2-compress-level.

--mangle-dos-filenames

--no-mangle-dos-filenames

Older version of Windows cannot handle filenames with more than one dot. --mangle-dos-filenames causes GnuPG to replace (rather than add to) the extension of an output filename to avoid this problem. This option is off by default and has no effect on non-Windows platforms.

--ask-cert-level

--no-ask-cert-level

When making a key signature, prompt for a certification level. If this option is not specified, the certification level used is set via --default-cert-level. See --default-cert-level for information on the specific levels and how they are used. --no-ask-cert-level disables this option. This option defaults to no.

--default-cert-level n

The default to use for the check level when signing a key.

0 means you make no particular claim as to how carefully you verified the key.

1 means you believe the key is owned by the person who claims to own it but you could not, or did not verify the key at all. This is useful for a "persona" verification, where you sign the key of a pseudonymous user.

2 means you did casual verification of the key. For example, this could mean that you verified the key fingerprint and checked the user ID on the key against a photo ID.

3 means you did extensive verification of the key. For example, this could mean that you verified the key fingerprint with the owner of the key in person, and that you checked, by means of a hard to forge document with a photo ID (such as a passport) that the name of the key owner matches the name in the user ID on the key, and finally that you verified (by exchange of email) that the email address on the key belongs to the key owner.

Note that the examples given above for levels 2 and 3 are just that: examples. In the end, it is up to you to decide just what "casual" and "extensive" mean to you.

This option defaults to 0 (no particular claim).

--min-cert-level

When building the trust database, treat any signatures with a certification level below this as invalid. Defaults to 2, which disregards level 1 signatures. Note that level 0 "no particular claim" signatures are always accepted.

--trusted-key long key ID

Assume that the specified key (which must be given as a full 8 byte key ID) is as trustworthy as one of your own secret keys. This option is useful if you don’t want to keep your secret keys (or one of them) online but still want to be able to check the validity of a given recipient’s or signator’s key.

--trust-model pgp|classic|tofu|tofu+pgp|direct|always|auto

Set what trust model GnuPG should follow. The models are:

pgp

This is the Web of Trust combined with trust signatures as used in PGP 5.x and later. This is the default trust model when creating a new trust database.

classic

This is the standard Web of Trust as introduced by PGP 2.

tofu

TOFU stands for Trust On First Use. In this trust model, the first time a key is seen, it is memorized. If later another key is seen with a user id with the same email address, a warning is displayed indicating that there is a conflict and that the key might be a forgery and an attempt at a man-in-the-middle attack.

Because a potential attacker is able to control the email address and thereby circumvent the conflict detection algorithm by using an email address that is similar in appearance to a trusted email address, whenever a message is verified, statistics about the number of messages signed with the key are shown. In this way, a user can easily identify attacks using fake keys for regular correspondents.

When compared with the Web of Trust, TOFU offers significantly weaker security guarantees. In particular, TOFU only helps ensure consistency (that is, that the binding between a key and email address doesn’t change). A major advantage of TOFU is that it requires little maintenance to use correctly. To use the web of trust properly, you need to actively sign keys and mark users as trusted introducers. This is a time-consuming process and anecdotal evidence suggests that even security-conscious users rarely take the time to do this thoroughly and instead rely on an ad-hoc TOFU process.

In the TOFU model, policies are associated with bindings between keys and email addresses (which are extracted from user ids and normalized). There are five policies, which can be set manually using the --tofu-policy option. The default policy can be set using the --tofu-default-policy policy.

The TOFU policies are: auto, good, unknown, bad and ask. The auto policy is used by default (unless overridden by --tofu-default-policy) and marks a binding as marginally trusted. The good, unknown and bad policies mark a binding as fully trusted, as having unknown trust or as having trust never, respectively. The unknown policy is useful for just using TOFU to detect conflicts, but to never assign positive trust to a binding. The final policy, ask prompts the user to indicate the binding’s trust. If batch mode is enabled (or input is inappropriate in the context), then the user is not prompted and the undefined trust level is returned.

tofu+pgp

This trust model combines TOFU with the Web of Trust. This is done by computing the trust level for each model and then taking the maximum trust level where the trust levels are ordered as follows: unknown < undefined < marginal < fully < ultimate < expired < never.

By setting --tofu-default-policy=unknown, this model can be used to implement the web of trust with TOFU’s conflict detection algorithm, but without its assignment of positive trust values, which some security-conscious users don’t like.

direct

Key validity is set directly by the user and not calculated via the Web of Trust.

always

Skip key validation and assume that used keys are always fully valid. You generally won’t use this unless you are using some external validation scheme. This option also suppresses the "[uncertain]" tag printed with signature checks when there is no evidence that the user ID is bound to the key. Note that this trust model still does not allow the use of expired, revoked, or disabled keys.

auto

Select the trust model depending on whatever the internal trust database says. This is the default model if such a database already exists.

--auto-key-locate parameters

--no-auto-key-locate

GnuPG can automatically locate and retrieve keys as needed using this option. This happens when encrypting to an email address (in the "user@example.com" form), and there are no user@example.com keys on the local keyring. This option takes any number of the following mechanisms, in the order they are to be tried:

cert

Locate a key using DNS CERT, as specified in rfc4398.

pka

Locate a key using DNS PKA.

dane

Locate a key using DANE, as specified in draft-ietf-dane-openpgpkey-05.txt.

wkd

Locate a key using the Web Key Directory protocol. This is an experimental method and semantics may change.

ldap

Using DNS Service Discovery, check the domain in question for any LDAP keyservers to use. If this fails, attempt to locate the key using the PGP Universal method of checking ‘ldap://keys.(thedomain)’.

keyserver

Locate a key using whatever keyserver is defined using the --keyserver option.

keyserver-URL

In addition, a keyserver URL as used in the --keyserver option may be used here to query that particular keyserver.

local

Locate the key using the local keyrings. This mechanism allows the user to select the order a local key lookup is done. Thus using ‘--auto-key-locate local’ is identical to --no-auto-key-locate.

nodefault

This flag disables the standard local key lookup, done before any of the mechanisms defined by the --auto-key-locate are tried. The position of this mechanism in the list does not matter. It is not required if local is also used.

clear

Clear all defined mechanisms. This is useful to override mechanisms given in a config file.

--auto-key-retrieve

--no-auto-key-retrieve

This option enables the automatic retrieving of keys from a keyserver when verifying signatures made by keys that are not on the local keyring.

If the method "wkd" is included in the list of methods given to auto-key-locate, the Signer’s User ID is part of the signature, and the option --disable-signer-uid is not used, the "wkd" method may also be used to retrieve a key.

Note that this option makes a "web bug" like behavior possible. Keyserver or Web Key Directory operators can see which keys you request, so by sending you a message signed by a brand new key (which you naturally will not have on your local keyring), the operator can tell both your IP address and the time when you verified the signature.

--keyid-format none|short|0xshort|long|0xlong

Select how to display key IDs. "none" does not show the key ID at all but shows the fingerprint in a separate line. "short" is the traditional 8-character key ID. "long" is the more accurate (but less convenient) 16-character key ID. Add an "0x" to either to include an "0x" at the beginning of the key ID, as in 0x99242560. Note that this option is ignored if the option --with-colons is used.

--keyserver name

This option is deprecated - please use the --keyserver in dirmngr.conf instead.

Use name as your keyserver. This is the server that --recv-keys, --send-keys, and --search-keys will communicate with to receive keys from, send keys to, and search for keys on. The format of the name is a URI: ‘scheme:[//]keyservername[:port]’ The scheme is the type of keyserver: "hkp" for the HTTP (or compatible) keyservers, "ldap" for the LDAP keyservers, or "mailto" for the Graff email keyserver. Note that your particular installation of GnuPG may have other keyserver types available as well. Keyserver schemes are case-insensitive. After the keyserver name, optional keyserver configuration options may be provided. These are the same as the global --keyserver-options from below, but apply only to this particular keyserver.

Most keyservers synchronize with each other, so there is generally no need to send keys to more than one server. The keyserver hkp://keys.gnupg.net uses round robin DNS to give a different keyserver each time you use it.

--keyserver-options name=value

This is a space or comma delimited string that gives options for the keyserver. Options can be prefixed with a ‘no-’ to give the opposite meaning. Valid import-options or export-options may be used here as well to apply to importing (--recv-key) or exporting (--send-key) a key from a keyserver. While not all options are available for all keyserver types, some common options are:

include-revoked

When searching for a key with --search-keys, include keys that are marked on the keyserver as revoked. Note that not all keyservers differentiate between revoked and unrevoked keys, and for such keyservers this option is meaningless. Note also that most keyservers do not have cryptographic verification of key revocations, and so turning this option off may result in skipping keys that are incorrectly marked as revoked.

include-disabled

When searching for a key with --search-keys, include keys that are marked on the keyserver as disabled. Note that this option is not used with HKP keyservers.

auto-key-retrieve

This is the same as the option auto-key-retrieve.

honor-keyserver-url

When using --refresh-keys, if the key in question has a preferred keyserver URL, then use that preferred keyserver to refresh the key from. In addition, if auto-key-retrieve is set, and the signature being verified has a preferred keyserver URL, then use that preferred keyserver to fetch the key from. Note that this option introduces a "web bug": The creator of the key can see when the keys is refreshed. Thus this option is not enabled by default.

honor-pka-record

If --auto-key-retrieve is used, and the signature being verified has a PKA record, then use the PKA information to fetch the key. Defaults to "yes".

include-subkeys

When receiving a key, include subkeys as potential targets. Note that this option is not used with HKP keyservers, as they do not support retrieving keys by subkey id.

timeout

Tell the keyserver helper program how long (in seconds) to try and perform a keyserver action before giving up. Note that performing multiple actions at the same time uses this timeout value per action. For example, when retrieving multiple keys via --recv-keys, the timeout applies separately to each key retrieval, and not to the --recv-keys command as a whole. Defaults to 30 seconds.

http-proxy=value

This options is deprecated. Set the proxy to use for HTTP and HKP keyservers. This overrides any proxy defined in dirmngr.conf.

verbose

This option has no more function since GnuPG 2.1. Use the dirmngr configuration options instead.

debug

This option has no more function since GnuPG 2.1. Use the dirmngr configuration options instead.

check-cert

This option has no more function since GnuPG 2.1. Use the dirmngr configuration options instead.

ca-cert-file

This option has no more function since GnuPG 2.1. Use the dirmngr configuration options instead.

--completes-needed n

Number of completely trusted users to introduce a new key signer (defaults to 1).

--marginals-needed n

Number of marginally trusted users to introduce a new key signer (defaults to 3)

--tofu-default-policy auto|good|unknown|bad|ask

The default TOFU policy (defaults to auto). For more information about the meaning of this option, See trust-model-tofu.

--max-cert-depth n

Maximum depth of a certification chain (default is 5).

--no-sig-cache

Do not cache the verification status of key signatures. Caching gives a much better performance in key listings. However, if you suspect that your public keyring is not save against write modifications, you can use this option to disable the caching. It probably does not make sense to disable it because all kind of damage can be done if someone else has write access to your public keyring.

--auto-check-trustdb

--no-auto-check-trustdb

If GnuPG feels that its information about the Web of Trust has to be updated, it automatically runs the --check-trustdb command internally. This may be a time consuming process. --no-auto-check-trustdb disables this option.

--use-agent

--no-use-agent

This is dummy option. gpg2 always requires the agent.

--gpg-agent-info

This is dummy option. It has no effect when used with gpg2.

--agent-program file

Specify an agent program to be used for secret key operations. The default value is determined by running gpgconf with the option --list-dirs. Note that the pipe symbol (|) is used for a regression test suite hack and may thus not be used in the file name.

--dirmngr-program file

Specify a dirmngr program to be used for keyserver access. The default value is /usr/bin/dirmngr.

--no-autostart

Do not start the gpg-agent or the dirmngr if it has not yet been started and its service is required. This option is mostly useful on machines where the connection to gpg-agent has been redirected to another machines. If dirmngr is required on the remote machine, it may be started manually using gpgconf --launch dirmngr.

--lock-once

Lock the databases the first time a lock is requested and do not release the lock until the process terminates.

--lock-multiple

Release the locks every time a lock is no longer needed. Use this to override a previous --lock-once from a config file.

--lock-never

Disable locking entirely. This option should be used only in very special environments, where it can be assured that only one process is accessing those files. A bootable floppy with a stand-alone encryption system will probably use this. Improper usage of this option may lead to data and key corruption.

--exit-on-status-write-error

This option will cause write errors on the status FD to immediately terminate the process. That should in fact be the default but it never worked this way and thus we need an option to enable this, so that the change won’t break applications which close their end of a status fd connected pipe too early. Using this option along with --enable-progress-filter may be used to cleanly cancel long running gpg operations.

--limit-card-insert-tries n

With n greater than 0 the number of prompts asking to insert a smartcard gets limited to N-1. Thus with a value of 1 gpg won’t at all ask to insert a card if none has been inserted at startup. This option is useful in the configuration file in case an application does not know about the smartcard support and waits ad infinitum for an inserted card.

--no-random-seed-file

GnuPG uses a file to store its internal random pool over invocations. This makes random generation faster; however sometimes write operations are not desired. This option can be used to achieve that with the cost of slower random generation.

--no-greeting

Suppress the initial copyright message.

--no-secmem-warning

Suppress the warning about "using insecure memory".

--no-permission-warning

Suppress the warning about unsafe file and home directory (--homedir) permissions. Note that the permission checks that GnuPG performs are not intended to be authoritative, but rather they simply warn about certain common permission problems. Do not assume that the lack of a warning means that your system is secure.

Note that the warning for unsafe --homedir permissions cannot be suppressed in the gpg.conf file, as this would allow an attacker to place an unsafe gpg.conf file in place, and use this file to suppress warnings about itself. The --homedir permissions warning may only be suppressed on the command line.

--no-mdc-warning

Suppress the warning about missing MDC integrity protection.

--require-secmem

--no-require-secmem

Refuse to run if GnuPG cannot get secure memory. Defaults to no (i.e. run, but give a warning).

--require-cross-certification

--no-require-cross-certification

When verifying a signature made from a subkey, ensure that the cross certification "back signature" on the subkey is present and valid. This protects against a subtle attack against subkeys that can sign. Defaults to --require-cross-certification for gpg2.

--expert

--no-expert

Allow the user to do certain nonsensical or "silly" things like signing an expired or revoked key, or certain potentially incompatible things like generating unusual key types. This also disables certain warning messages about potentially incompatible actions. As the name implies, this option is for experts only. If you don’t fully understand the implications of what it allows you to do, leave this off. --no-expert disables this option.

4.2.2 Key related options

--recipient name

-r

Encrypt for user id name. If this option or --hidden-recipient is not specified, GnuPG asks for the user-id unless --default-recipient is given.

--hidden-recipient name

-R

Encrypt for user ID name, but hide the key ID of this user’s key. This option helps to hide the receiver of the message and is a limited countermeasure against traffic analysis. If this option or --recipient is not specified, GnuPG asks for the user ID unless --default-recipient is given.

--recipient-file file

-f

This option is similar to --recipient except that it encrypts to a key stored in the given file. file must be the name of a file containing exactly one key. gpg assumes that the key in this file is fully valid.

--hidden-recipient-file file

-F

This option is similar to --hidden-recipient except that it encrypts to a key stored in the given file. file must be the name of a file containing exactly one key. gpg assumes that the key in this file is fully valid.

--encrypt-to name

Same as --recipient but this one is intended for use in the options file and may be used with your own user-id as an "encrypt-to-self". These keys are only used when there are other recipients given either by use of --recipient or by the asked user id. No trust checking is performed for these user ids and even disabled keys can be used.

--hidden-encrypt-to name

Same as --hidden-recipient but this one is intended for use in the options file and may be used with your own user-id as a hidden "encrypt-to-self". These keys are only used when there are other recipients given either by use of --recipient or by the asked user id. No trust checking is performed for these user ids and even disabled keys can be used.

--no-encrypt-to

Disable the use of all --encrypt-to and --hidden-encrypt-to keys.

--group name=value1

Sets up a named group, which is similar to aliases in email programs. Any time the group name is a recipient (-r or --recipient), it will be expanded to the values specified. Multiple groups with the same name are automatically merged into a single group.

The values are key IDs or fingerprints, but any key description is accepted. Note that a value with spaces in it will be treated as two different values. Note also there is only one level of expansion — you cannot make an group that points to another group. When used from the command line, it may be necessary to quote the argument to this option to prevent the shell from treating it as multiple arguments.

--ungroup name

Remove a given entry from the --group list.

--no-groups

Remove all entries from the --group list.

--local-user name

-u

Use name as the key to sign with. Note that this option overrides --default-key.

--sender mbox

This option has two purposes. mbox must either be a complete user id with a proper mail address or just a mail address. When creating a signature this option tells gpg the user id of a key used to make a signature if the key was not directly specified by a user id. When verifying a signature the mbox is used to restrict the information printed by the TOFU code to matching user ids.

--try-secret-key name

For hidden recipients GPG needs to know the keys to use for trial decryption. The key set with --default-key is always tried first, but this is often not sufficient. This option allows setting more keys to be used for trial decryption. Although any valid user-id specification may be used for name it makes sense to use at least the long keyid to avoid ambiguities. Note that gpg-agent might pop up a pinentry for a lot keys to do the trial decryption. If you want to stop all further trial decryption you may use close-window button instead of the cancel button.

--try-all-secrets

Don’t look at the key ID as stored in the message but try all secret keys in turn to find the right decryption key. This option forces the behaviour as used by anonymous recipients (created by using --throw-keyids or --hidden-recipient) and might come handy in case where an encrypted message contains a bogus key ID.

--skip-hidden-recipients

--no-skip-hidden-recipients

During decryption skip all anonymous recipients. This option helps in the case that people use the hidden recipients feature to hide there own encrypt-to key from others. If oneself has many secret keys this may lead to a major annoyance because all keys are tried in turn to decrypt something which was not really intended for it. The drawback of this option is that it is currently not possible to decrypt a message which includes real anonymous recipients.

4.2.3 Input and Output

--armor

-a

Create ASCII armored output. The default is to create the binary OpenPGP format.

--no-armor

Assume the input data is not in ASCII armored format.

--output file

-o file

Write output to file.

--max-output n

This option sets a limit on the number of bytes that will be generated when processing a file. Since OpenPGP supports various levels of compression, it is possible that the plaintext of a given message may be significantly larger than the original OpenPGP message. While GnuPG works properly with such messages, there is often a desire to set a maximum file size that will be generated before processing is forced to stop by the OS limits. Defaults to 0, which means "no limit".

--input-size-hint n

This option can be used to tell GPG the size of the input data in bytes. n must be a positive base-10 number. This option is only useful if the input is not taken from a file. GPG may use thos hint to optimize its buffer allocation strategy. It is also used by the --status-fd line “PROGRESS” to provide a value for “total” if that is not available by other means.

--import-options parameters

This is a space or comma delimited string that gives options for importing keys. Options can be prepended with a ‘no-’ to give the opposite meaning. The options are:

import-local-sigs

Allow importing key signatures marked as "local". This is not generally useful unless a shared keyring scheme is being used. Defaults to no.

keep-ownertrust

Normally possible still existing ownertrust values of a key are cleared if a key is imported. This is in general desirable so that a formerly deleted key does not automatically gain an ownertrust values merely due to import. On the other hand it is sometimes necessary to re-import a trusted set of keys again but keeping already assigned ownertrust values. This can be achived by using this option.

repair-pks-subkey-bug

During import, attempt to repair the damage caused by the PKS keyserver bug (pre version 0.9.6) that mangles keys with multiple subkeys. Note that this cannot completely repair the damaged key as some crucial data is removed by the keyserver, but it does at least give you back one subkey. Defaults to no for regular --import and to yes for keyserver --recv-keys.

import-show

Show a listing of the key as imported right before it is stored. This can be combined with the option --dry-run to only look at keys.

import-export

Run the entire import code but instead of storing the key to the local keyring write it to the output. The export options export-pka and export-dane affect the output. This option can be used to remove all invalid parts from a key without the need to store it.

merge-only

During import, allow key updates to existing keys, but do not allow any new keys to be imported. Defaults to no.

import-clean

After import, compact (remove all signatures except the self-signature) any user IDs from the new key that are not usable. Then, remove any signatures from the new key that are not usable. This includes signatures that were issued by keys that are not present on the keyring. This option is the same as running the --edit-key command "clean" after import. Defaults to no.

import-minimal

Import the smallest key possible. This removes all signatures except the most recent self-signature on each user ID. This option is the same as running the --edit-key command "minimize" after import. Defaults to no.

--import-filter name=expr

--export-filter name=expr

These options define an import/export filter which are applied to the imported/exported keyblock right before it will be stored/written. name defines the type of filter to use, expr the expression to evaluate. The option can be used several times which then appends more expression to the same name.

The available filter types are:

keep-uid

This filter will keep a user id packet and its dependent packets in the keyblock if the expression evaluates to true.

drop-sig

This filter drops the selected key signatures on user ids. Self-signatures are not consideres. Currently only implemented for –import-filter.

For the syntax of the expression see the chapter "FILTER EXPRESSIONS". The property names for the expressions depend on the actual filter type and are indicated in the following table.

The available properties are:

uid

A string with the user id. (keep-uid)

mbox

The addr-spec part of a user id with mailbox or the empty string. (keep-uid)

primary

Boolean indicating whether the user id is the primary one. (keep-uid)

sig_created

sig_created_d

The first is the timestamp a signature packet was created. The second is the same but given as an ISO string, e.g. "2016-08-17". (drop-sig)

sig_algo

A number with the public key algorithm of a signature packet. (drop-sig)

sig_digest_algo

A number with the digest algorithm of a signature packet. (drop-sig)

--export-options parameters

This is a space or comma delimited string that gives options for exporting keys. Options can be prepended with a ‘no-’ to give the opposite meaning. The options are:

export-local-sigs

Allow exporting key signatures marked as "local". This is not generally useful unless a shared keyring scheme is being used. Defaults to no.

export-attributes

Include attribute user IDs (photo IDs) while exporting. This is useful to export keys if they are going to be used by an OpenPGP program that does not accept attribute user IDs. Defaults to yes.

export-sensitive-revkeys

Include designated revoker information that was marked as "sensitive". Defaults to no.

export-clean

Compact (remove all signatures from) user IDs on the key being exported if the user IDs are not usable. Also, do not export any signatures that are not usable. This includes signatures that were issued by keys that are not present on the keyring. This option is the same as running the --edit-key command "clean" before export except that the local copy of the key is not modified. Defaults to no.

export-minimal

Export the smallest key possible. This removes all signatures except the most recent self-signature on each user ID. This option is the same as running the --edit-key command "minimize" before export except that the local copy of the key is not modified. Defaults to no.

export-pka

Instead of outputting the key material output PKA records suitable to put into DNS zone files. An ORIGIN line is printed before each record to allow diverting the records to the corresponding zone file.

export-dane

Instead of outputting the key material output OpenPGP DANE records suitable to put into DNS zone files. An ORIGIN line is printed before each record to allow diverting the records to the corresponding zone file.

--with-colons

Print key listings delimited by colons. Note that the output will be encoded in UTF-8 regardless of any --display-charset setting. This format is useful when GnuPG is called from scripts and other programs as it is easily machine parsed. The details of this format are documented in the file doc/DETAILS, which is included in the GnuPG source distribution.

--fixed-list-mode

Do not merge primary user ID and primary key in --with-colon listing mode and print all timestamps as seconds since 1970-01-01. Since GnuPG 2.0.10, this mode is always used and thus this option is obsolete; it does not harm to use it though.

--legacy-list-mode

Revert to the pre-2.1 public key list mode. This only affects the human readable output and not the machine interface (i.e. --with-colons). Note that the legacy format does not convey suitable information for elliptic curves.

--with-fingerprint

Same as the command --fingerprint but changes only the format of the output and may be used together with another command.

--with-subkey-fingerprint

If a fingerprint is printed for the primary key, this option forces printing of the fingerprint for all subkeys. This could also be achieved by using the --with-fingerprint twice but by using this option along with keyid-format "none" a compact fingerprint is printed.

--with-icao-spelling

Print the ICAO spelling of the fingerprint in addition to the hex digits.

--with-keygrip

Include the keygrip in the key listings. In --with-colons mode this is implicitly enable for secret keys.

--with-wkd-hash

Print a Web Key Directory indentifier along with each user ID in key listings. This is an experimental feature and semantics may change.

--with-secret

Include info about the presence of a secret key in public key listings done with --with-colons.

4.2.4 OpenPGP protocol specific options.

-t, --textmode

--no-textmode

Treat input files as text and store them in the OpenPGP canonical text form with standard "CRLF" line endings. This also sets the necessary flags to inform the recipient that the encrypted or signed data is text and may need its line endings converted back to whatever the local system uses. This option is useful when communicating between two platforms that have different line ending conventions (UNIX-like to Mac, Mac to Windows, etc). --no-textmode disables this option, and is the default.

--force-v3-sigs

--no-force-v3-sigs

--force-v4-certs

--no-force-v4-certs

These options are obsolete and have no effect since GnuPG 2.1.

--force-mdc

Force the use of encryption with a modification detection code. This is always used with the newer ciphers (those with a blocksize greater than 64 bits), or if all of the recipient keys indicate MDC support in their feature flags.

--disable-mdc

Disable the use of the modification detection code. Note that by using this option, the encrypted message becomes vulnerable to a message modification attack.

--disable-signer-uid

By default the user ID of the signing key is embedded in the data signature. As of now this is only done if the signing key has been specified with local-user using a mail address. This information can be helpful for verifier to locate the key; see option --auto-key-retrieve.

--personal-cipher-preferences string

Set the list of personal cipher preferences to string. Use gpg2 --version to get a list of available algorithms, and use none to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked cipher in this list is also used for the --symmetric encryption command.

--personal-digest-preferences string

Set the list of personal digest preferences to string. Use gpg2 --version to get a list of available algorithms, and use none to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked digest algorithm in this list is also used when signing without encryption (e.g. --clearsign or --sign).

--personal-compress-preferences string

Set the list of personal compression preferences to string. Use gpg2 --version to get a list of available algorithms, and use none to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked compression algorithm in this list is also used when there are no recipient keys to consider (e.g. --symmetric).

--s2k-cipher-algo name

Use name as the cipher algorithm for symmetric encryption with a passphrase if --personal-cipher-preferences and --cipher-algo are not given. The default is AES-128.

--s2k-digest-algo name

Use name as the digest algorithm used to mangle the passphrases for symmetric encryption. The default is SHA-1.

--s2k-mode n

Selects how passphrases for symmetric encryption are mangled. If n is 0 a plain passphrase (which is in general not recommended) will be used, a 1 adds a salt (which should not be used) to the passphrase and a 3 (the default) iterates the whole process a number of times (see --s2k-count).

--s2k-count n

Specify how many times the passphrases mangling for symmetric encryption is repeated. This value may range between 1024 and 65011712 inclusive. The default is inquired from gpg-agent. Note that not all values in the 1024-65011712 range are legal and if an illegal value is selected, GnuPG will round up to the nearest legal value. This option is only meaningful if --s2k-mode is set to the default of 3.

4.2.5 Compliance options

These options control what GnuPG is compliant to. Only one of these options may be active at a time. Note that the default setting of this is nearly always the correct one. See the INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS section below before using one of these options.

--gnupg

Use standard GnuPG behavior. This is essentially OpenPGP behavior (see --openpgp), but with some additional workarounds for common compatibility problems in different versions of PGP. This is the default option, so it is not generally needed, but it may be useful to override a different compliance option in the gpg.conf file.

--openpgp

Reset all packet, cipher and digest options to strict OpenPGP behavior. Use this option to reset all previous options like --s2k-*, --cipher-algo, --digest-algo and --compress-algo to OpenPGP compliant values. All PGP workarounds are disabled.

--rfc4880

Reset all packet, cipher and digest options to strict RFC-4880 behavior. Note that this is currently the same thing as --openpgp.

--rfc4880bis

Enable experimental features from proposed updates to RFC-4880. This option can be used in addition to the other compliance options. Warning: The behavior may change with any GnuPG release and created keys or data may not be usable with future GnuPG versions.

--rfc2440

Reset all packet, cipher and digest options to strict RFC-2440 behavior.

--pgp6

Set up all options to be as PGP 6 compliant as possible. This restricts you to the ciphers IDEA (if the IDEA plugin is installed), 3DES, and CAST5, the hashes MD5, SHA1 and RIPEMD160, and the compression algorithms none and ZIP. This also disables –throw-keyids, and making signatures with signing subkeys as PGP 6 does not understand signatures made by signing subkeys.

This option implies --disable-mdc --escape-from-lines.

--pgp7

Set up all options to be as PGP 7 compliant as possible. This is identical to --pgp6 except that MDCs are not disabled, and the list of allowable ciphers is expanded to add AES128, AES192, AES256, and TWOFISH.

--pgp8

Set up all options to be as PGP 8 compliant as possible. PGP 8 is a lot closer to the OpenPGP standard than previous versions of PGP, so all this does is disable --throw-keyids and set --escape-from-lines. All algorithms are allowed except for the SHA224, SHA384, and SHA512 digests.

4.2.6 Doing things one usually doesn’t want to do.

-n

--dry-run

Don’t make any changes (this is not completely implemented).

--list-only

Changes the behaviour of some commands. This is like --dry-run but different in some cases. The semantic of this command may be extended in the future. Currently it only skips the actual decryption pass and therefore enables a fast listing of the encryption keys.

-i

--interactive

Prompt before overwriting any files.

--debug-level level

Select the debug level for investigating problems. level may be a numeric value or by a keyword:

none

No debugging at all. A value of less than 1 may be used instead of the keyword.

basic

Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

advanced

More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

expert

Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

guru

All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

--debug flags

Set debugging flags. All flags are or-ed and flags may be given in C syntax (e.g. 0x0042) or as a comma separated list of flag names. To get a list of all supported flags the single word "help" can be used.

--debug-all

Set all useful debugging flags.

--debug-iolbf

Set stdout into line buffered mode. This option is only honored when given on the command line.

--faked-system-time epoch

This option is only useful for testing; it sets the system time back or forth to epoch which is the number of seconds elapsed since the year 1970. Alternatively epoch may be given as a full ISO time string (e.g. "20070924T154812").

--enable-progress-filter

Enable certain PROGRESS status outputs. This option allows frontends to display a progress indicator while gpg is processing larger files. There is a slight performance overhead using it.

--status-fd n

Write special status strings to the file descriptor n. See the file DETAILS in the documentation for a listing of them.

--status-file file

Same as --status-fd, except the status data is written to file file.

--logger-fd n

Write log output to file descriptor n and not to STDERR.

--log-file file

--logger-file file

Same as --logger-fd, except the logger data is written to file file. Note that --log-file is only implemented for GnuPG-2.

--attribute-fd n

Write attribute subpackets to the file descriptor n. This is most useful for use with --status-fd, since the status messages are needed to separate out the various subpackets from the stream delivered to the file descriptor.

--attribute-file file

Same as --attribute-fd, except the attribute data is written to file file.

--comment string

--no-comments

Use string as a comment string in clear text signatures and ASCII armored messages or keys (see --armor). The default behavior is not to use a comment string. --comment may be repeated multiple times to get multiple comment strings. --no-comments removes all comments. It is a good idea to keep the length of a single comment below 60 characters to avoid problems with mail programs wrapping such lines. Note that comment lines, like all other header lines, are not protected by the signature.

--emit-version

--no-emit-version

Force inclusion of the version string in ASCII armored output. If given once only the name of the program and the major number is emitted, given twice the minor is also emitted, given triple the micro is added, and given quad an operating system identification is also emitted. --no-emit-version (default) disables the version line.

--sig-notation name=value

--cert-notation name=value

-N, --set-notation name=value

Put the name value pair into the signature as notation data. name must consist only of printable characters or spaces, and must contain a ’@’ character in the form keyname@domain.example.com (substituting the appropriate keyname and domain name, of course). This is to help prevent pollution of the IETF reserved notation namespace. The --expert flag overrides the ’@’ check. value may be any printable string; it will be encoded in UTF8, so you should check that your --display-charset is set correctly. If you prefix name with an exclamation mark (!), the notation data will be flagged as critical (rfc4880:5.2.3.16). --sig-notation sets a notation for data signatures. --cert-notation sets a notation for key signatures (certifications). --set-notation sets both.

There are special codes that may be used in notation names. "%k" will be expanded into the key ID of the key being signed, "%K" into the long key ID of the key being signed, "%f" into the fingerprint of the key being signed, "%s" into the key ID of the key making the signature, "%S" into the long key ID of the key making the signature, "%g" into the fingerprint of the key making the signature (which might be a subkey), "%p" into the fingerprint of the primary key of the key making the signature, "%c" into the signature count from the OpenPGP smartcard, and "%%" results in a single "%". %k, %K, and %f are only meaningful when making a key signature (certification), and %c is only meaningful when using the OpenPGP smartcard.

--sig-policy-url string

--cert-policy-url string

--set-policy-url string

Use string as a Policy URL for signatures (rfc4880:5.2.3.20). If you prefix it with an exclamation mark (!), the policy URL packet will be flagged as critical. --sig-policy-url sets a policy url for data signatures. --cert-policy-url sets a policy url for key signatures (certifications). --set-policy-url sets both.

The same %-expandos used for notation data are available here as well.

--sig-keyserver-url string

Use string as a preferred keyserver URL for data signatures. If you prefix it with an exclamation mark (!), the keyserver URL packet will be flagged as critical.

The same %-expandos used for notation data are available here as well.

--set-filename string

Use string as the filename which is stored inside messages. This overrides the default, which is to use the actual filename of the file being encrypted. Using the empty string for string effectively removes the filename from the output.

--for-your-eyes-only

--no-for-your-eyes-only

Set the ‘for your eyes only’ flag in the message. This causes GnuPG to refuse to save the file unless the --output option is given, and PGP to use a "secure viewer" with a claimed Tempest-resistant font to display the message. This option overrides --set-filename. --no-for-your-eyes-only disables this option.

--use-embedded-filename

--no-use-embedded-filename

Try to create a file with a name as embedded in the data. This can be a dangerous option as it enables overwriting files. Defaults to no.

--cipher-algo name

Use name as cipher algorithm. Running the program with the command --version yields a list of supported algorithms. If this is not used the cipher algorithm is selected from the preferences stored with the key. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. --personal-cipher-preferences is the safe way to accomplish the same thing.

--digest-algo name

Use name as the message digest algorithm. Running the program with the command --version yields a list of supported algorithms. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. --personal-digest-preferences is the safe way to accomplish the same thing.

--compress-algo name

Use compression algorithm name. "zlib" is RFC-1950 ZLIB compression. "zip" is RFC-1951 ZIP compression which is used by PGP. "bzip2" is a more modern compression scheme that can compress some things better than zip or zlib, but at the cost of more memory used during compression and decompression. "uncompressed" or "none" disables compression. If this option is not used, the default behavior is to examine the recipient key preferences to see which algorithms the recipient supports. If all else fails, ZIP is used for maximum compatibility.

ZLIB may give better compression results than ZIP, as the compression window size is not limited to 8k. BZIP2 may give even better compression results than that, but will use a significantly larger amount of memory while compressing and decompressing. This may be significant in low memory situations. Note, however, that PGP (all versions) only supports ZIP compression. Using any algorithm other than ZIP or "none" will make the message unreadable with PGP. In general, you do not want to use this option as it allows you to violate the OpenPGP standard. --personal-compress-preferences is the safe way to accomplish the same thing.

--cert-digest-algo name

Use name as the message digest algorithm used when signing a key. Running the program with the command --version yields a list of supported algorithms. Be aware that if you choose an algorithm that GnuPG supports but other OpenPGP implementations do not, then some users will not be able to use the key signatures you make, or quite possibly your entire key.

--disable-cipher-algo name

Never allow the use of name as cipher algorithm. The given name will not be checked so that a later loaded algorithm will still get disabled.

--disable-pubkey-algo name

Never allow the use of name as public key algorithm. The given name will not be checked so that a later loaded algorithm will still get disabled.

--throw-keyids

--no-throw-keyids

Do not put the recipient key IDs into encrypted messages. This helps to hide the receivers of the message and is a limited countermeasure against traffic analysis.² On the receiving side, it may slow down the decryption process because all available secret keys must be tried. --no-throw-keyids disables this option. This option is essentially the same as using --hidden-recipient for all recipients.

--not-dash-escaped

This option changes the behavior of cleartext signatures so that they can be used for patch files. You should not send such an armored file via email because all spaces and line endings are hashed too. You can not use this option for data which has 5 dashes at the beginning of a line, patch files don’t have this. A special armor header line tells GnuPG about this cleartext signature option.

--escape-from-lines

--no-escape-from-lines

Because some mailers change lines starting with "From " to ">From " it is good to handle such lines in a special way when creating cleartext signatures to prevent the mail system from breaking the signature. Note that all other PGP versions do it this way too. Enabled by default. --no-escape-from-lines disables this option.

--passphrase-repeat n

Specify how many times gpg2 will request a new passphrase be repeated. This is useful for helping memorize a passphrase. Defaults to 1 repetition.

--passphrase-fd n

Read the passphrase from file descriptor n. Only the first line will be read from file descriptor n. If you use 0 for n, the passphrase will be read from STDIN. This can only be used if only one passphrase is supplied.

Note that this passphrase is only used if the option --batch has also been given. This is different from GnuPG version 1.x.

--passphrase-file file

Read the passphrase from file file. Only the first line will be read from file file. This can only be used if only one passphrase is supplied. Obviously, a passphrase stored in a file is of questionable security if other users can read this file. Don’t use this option if you can avoid it. Note that this passphrase is only used if the option --batch has also been given. This is different from GnuPG version 1.x.

--passphrase string

Use string as the passphrase. This can only be used if only one passphrase is supplied. Obviously, this is of very questionable security on a multi-user system. Don’t use this option if you can avoid it. Note that this passphrase is only used if the option --batch has also been given. This is different from GnuPG version 1.x.

--pinentry-mode mode

Set the pinentry mode to mode. Allowed values for mode are:

default

Use the default of the agent, which is ask.

ask

Force the use of the Pinentry.

cancel

Emulate use of Pinentry’s cancel button.

error

Return a Pinentry error (“No Pinentry”).

loopback

Redirect Pinentry queries to the caller. Note that in contrast to Pinentry the user is not prompted again if he enters a bad password.

--command-fd n

This is a replacement for the deprecated shared-memory IPC mode. If this option is enabled, user input on questions is not expected from the TTY but from the given file descriptor. It should be used together with --status-fd. See the file doc/DETAILS in the source distribution for details on how to use it.

--command-file file

Same as --command-fd, except the commands are read out of file file

--allow-non-selfsigned-uid

--no-allow-non-selfsigned-uid

Allow the import and use of keys with user IDs which are not self-signed. This is not recommended, as a non self-signed user ID is trivial to forge. --no-allow-non-selfsigned-uid disables.

--allow-freeform-uid

Disable all checks on the form of the user ID while generating a new one. This option should only be used in very special environments as it does not ensure the de-facto standard format of user IDs.

--ignore-time-conflict

GnuPG normally checks that the timestamps associated with keys and signatures have plausible values. However, sometimes a signature seems to be older than the key due to clock problems. This option makes these checks just a warning. See also --ignore-valid-from for timestamp issues on subkeys.

--ignore-valid-from

GnuPG normally does not select and use subkeys created in the future. This option allows the use of such keys and thus exhibits the pre-1.0.7 behaviour. You should not use this option unless there is some clock problem. See also --ignore-time-conflict for timestamp issues with signatures.

--ignore-crc-error

The ASCII armor used by OpenPGP is protected by a CRC checksum against transmission errors. Occasionally the CRC gets mangled somewhere on the transmission channel but the actual content (which is protected by the OpenPGP protocol anyway) is still okay. This option allows GnuPG to ignore CRC errors.

--ignore-mdc-error

This option changes a MDC integrity protection failure into a warning. This can be useful if a message is partially corrupt, but it is necessary to get as much data as possible out of the corrupt message. However, be aware that a MDC protection failure may also mean that the message was tampered with intentionally by an attacker.

--allow-weak-digest-algos

Signatures made with known-weak digest algorithms are normally rejected with an “invalid digest algorithm” message. This option allows the verification of signatures made with such weak algorithms. MD5 is the only digest algorithm considered weak by default. See also --weak-digest to reject other digest algorithms.

--weak-digest name

Treat the specified digest algorithm as weak. Signatures made over weak digests algorithms are normally rejected. This option can be supplied multiple times if multiple algorithms should be considered weak. See also --allow-weak-digest-algos to disable rejection of weak digests. MD5 is always considered weak, and does not need to be listed explicitly.

--no-default-keyring

Do not add the default keyrings to the list of keyrings. Note that GnuPG will not operate without any keyrings, so if you use this option and do not provide alternate keyrings via --keyring or --secret-keyring, then GnuPG will still use the default public or secret keyrings.

--no-keyring

Do not add use any keyrings even if specified as options.

--skip-verify

Skip the signature verification step. This may be used to make the decryption faster if the signature verification is not needed.

--with-key-data

Print key listings delimited by colons (like --with-colons) and print the public key data.

--fast-list-mode

Changes the output of the list commands to work faster; this is achieved by leaving some parts empty. Some applications don’t need the user ID and the trust information given in the listings. By using this options they can get a faster listing. The exact behaviour of this option may change in future versions. If you are missing some information, don’t use this option.

--no-literal

This is not for normal use. Use the source to see for what it might be useful.

--set-filesize

This is not for normal use. Use the source to see for what it might be useful.

--show-session-key

Display the session key used for one message. See --override-session-key for the counterpart of this option.

We think that Key Escrow is a Bad Thing; however the user should have the freedom to decide whether to go to prison or to reveal the content of one specific message without compromising all messages ever encrypted for one secret key.

You can also use this option if you receive an encrypted message which is abusive or offensive, to prove to the administrators of the messaging system that the ciphertext transmitted corresponds to an inappropriate plaintext so they can take action against the offending user.

--override-session-key string

Don’t use the public key but the session key string. The format of this string is the same as the one printed by --show-session-key. This option is normally not used but comes handy in case someone forces you to reveal the content of an encrypted message; using this option you can do this without handing out the secret key.

--ask-sig-expire

--no-ask-sig-expire

When making a data signature, prompt for an expiration time. If this option is not specified, the expiration time set via --default-sig-expire is used. --no-ask-sig-expire disables this option.

--default-sig-expire

The default expiration time to use for signature expiration. Valid values are "0" for no expiration, a number followed by the letter d (for days), w (for weeks), m (for months), or y (for years) (for example "2m" for two months, or "5y" for five years), or an absolute date in the form YYYY-MM-DD. Defaults to "0".

--ask-cert-expire

--no-ask-cert-expire

When making a key signature, prompt for an expiration time. If this option is not specified, the expiration time set via --default-cert-expire is used. --no-ask-cert-expire disables this option.

--default-cert-expire

The default expiration time to use for key signature expiration. Valid values are "0" for no expiration, a number followed by the letter d (for days), w (for weeks), m (for months), or y (for years) (for example "2m" for two months, or "5y" for five years), or an absolute date in the form YYYY-MM-DD. Defaults to "0".

--allow-secret-key-import

This is an obsolete option and is not used anywhere.

--allow-multiple-messages

--no-allow-multiple-messages

Allow processing of multiple OpenPGP messages contained in a single file or stream. Some programs that call GPG are not prepared to deal with multiple messages being processed together, so this option defaults to no. Note that versions of GPG prior to 1.4.7 always allowed multiple messages.

Warning: Do not use this option unless you need it as a temporary workaround!

--enable-special-filenames

This options enables a mode in which filenames of the form -&n, where n is a non-negative decimal number, refer to the file descriptor n and not to a file with that name.

--no-expensive-trust-checks

Experimental use only.

--preserve-permissions

Don’t change the permissions of a secret keyring back to user read/write only. Use this option only if you really know what you are doing.

--default-preference-list string

Set the list of default preferences to string. This preference list is used for new keys and becomes the default for "setpref" in the edit menu.

--default-keyserver-url name

Set the default keyserver URL to name. This keyserver will be used as the keyserver URL when writing a new self-signature on a key, which includes key generation and changing preferences.

--list-config

Display various internal configuration parameters of GnuPG. This option is intended for external programs that call GnuPG to perform tasks, and is thus not generally useful. See the file doc/DETAILS in the source distribution for the details of which configuration items may be listed. --list-config is only usable with --with-colons set.

--list-gcrypt-config

Display various internal configuration parameters of Libgcrypt.

--gpgconf-list

This command is similar to --list-config but in general only internally used by the gpgconf tool.

--gpgconf-test

This is more or less dummy action. However it parses the configuration file and returns with failure if the configuration file would prevent gpg from startup. Thus it may be used to run a syntax check on the configuration file.

4.2.7 Deprecated options

--show-photos

--no-show-photos

Causes --list-keys, --list-sigs, --list-public-keys, --list-secret-keys, and verifying a signature to also display the photo ID attached to the key, if any. See also --photo-viewer. These options are deprecated. Use --list-options [no-]show-photos and/or --verify-options [no-]show-photos instead.

--show-keyring

Display the keyring name at the head of key listings to show which keyring a given key resides on. This option is deprecated: use --list-options [no-]show-keyring instead.

--always-trust

Identical to --trust-model always. This option is deprecated.

--show-notation

--no-show-notation

Show signature notations in the --list-sigs or --check-sigs listings as well as when verifying a signature with a notation in it. These options are deprecated. Use --list-options [no-]show-notation and/or --verify-options [no-]show-notation instead.

--show-policy-url

--no-show-policy-url

Show policy URLs in the --list-sigs or --check-sigs listings as well as when verifying a signature with a policy URL in it. These options are deprecated. Use --list-options [no-]show-policy-url and/or --verify-options [no-]show-policy-url instead.

4.3 Configuration files

There are a few configuration files to control certain aspects of gpg2’s operation. Unless noted, they are expected in the current home directory (see option --homedir).

gpg.conf

This is the standard configuration file read by gpg2 on startup. It may contain any valid long option; the leading two dashes may not be entered and the option may not be abbreviated. This default name may be changed on the command line (see gpg-option --options). You should backup this file.

Note that on larger installations, it is useful to put predefined files into the directory /usr/etc/skel/.gnupg so that newly created users start up with a working configuration. For existing users a small helper script is provided to create these files (see addgnupghome).

For internal purposes gpg2 creates and maintains a few other files; They all live in in the current home directory (see option --homedir). Only the gpg2 program may modify these files.

~/.gnupg

This is the default home directory which is used if neither the environment variable GNUPGHOME nor the option --homedir is given.

~/.gnupg/pubring.gpg

The public keyring. You should backup this file.

~/.gnupg/pubring.gpg.lock

The lock file for the public keyring.

~/.gnupg/pubring.kbx

The public keyring using a different format. This file is sharred with gpgsm. You should backup this file.

~/.gnupg/pubring.kbx.lock

The lock file for pubring.kbx.

~/.gnupg/secring.gpg

A secret keyring as used by GnuPG versions before 2.1. It is not used by GnuPG 2.1 and later.

~/.gnupg/secring.gpg.lock

The lock file for the secret keyring.

~/.gnupg/.gpg-v21-migrated

File indicating that a migration to GnuPG 2.1 has been done.

~/.gnupg/trustdb.gpg

The trust database. There is no need to backup this file; it is better to backup the ownertrust values (see option --export-ownertrust).

~/.gnupg/trustdb.gpg.lock

The lock file for the trust database.

~/.gnupg/random_seed

A file used to preserve the state of the internal random pool.

~/.gnupg/openpgp-revocs.d/

This is the directory where gpg stores pre-generated revocation certificates. The file name corresponds to the OpenPGP fingerprint of the respective key. It is suggested to backup those certificates and if the primary private key is not stored on the disk to move them to an external storage device. Anyone who can access theses files is able to revoke the corresponding key. You may want to print them out. You should backup all files in this directory and take care to keep this backup closed away.

/usr/share/gnupg/options.skel

The skeleton options file.

Operation is further controlled by a few environment variables:

HOME

Used to locate the default home directory.

GNUPGHOME

If set directory used instead of "~/.gnupg".

GPG_AGENT_INFO

This variable is obsolete; it was used by GnuPG versions before 2.1.

PINENTRY_USER_DATA

This value is passed via gpg-agent to pinentry. It is useful to convey extra information to a custom pinentry.

COLUMNS

LINES

Used to size some displays to the full size of the screen.

LANGUAGE

Apart from its use by GNU, it is used in the W32 version to override the language selection done through the Registry. If used and set to a valid and available language name (langid), the file with the translation is loaded from

gpgdir/gnupg.nls/langid.mo. Here gpgdir is the directory out of which the gpg binary has been loaded. If it can’t be loaded the Registry is tried and as last resort the native Windows locale system is used.

4.4 Examples

gpg -se -r Bob file

sign and encrypt for user Bob

gpg –clearsign file

make a clear text signature

gpg -sb file

make a detached signature

gpg -u 0x12345678 -sb file

make a detached signature with the key 0x12345678

gpg –list-keys user_ID

show keys

gpg –fingerprint user_ID

show fingerprint

gpg –verify pgpfile

gpg –verify sigfile

Verify the signature of the file but do not output the data. The second form is used for detached signatures, where sigfile is the detached signature (either ASCII armored or binary) and are the signed data; if this is not given, the name of the file holding the signed data is constructed by cutting off the extension (".asc" or ".sig") of sigfile or by asking the user for the filename.

FILTER EXPRESSIONS

The options --import-filter and --export-filter use expressions with this syntax (square brackets indicate an optional part and curly braces a repetition, white space between the elements are allowed):

  [lc] {[{flag}] PROPNAME op VALUE [lc]}

The name of a property (PROPNAME) may only consist of letters, digits and underscores. The description for the filter type describes which properties are defined. If an undefined property is used it evaluates to the empty string. Unless otherwise noted, the VALUE must always be given and may not be the empty string. No quoting is defined for the value, thus the value may not contain the strings && or ||, which are used as logical connection operators. The flag -- can be used to remove this restriction.

Numerical values are computed as long int; standard C notation applies. lc is the logical connection operator; either && for a conjunction or || for a disjunction. A conjunction is assumed at the begin of an expression. Conjunctions have higher precedence than disjunctions. If VALUE starts with one of the characters used in any op a space after the op is required.

The supported operators (op) are:

=~

Substring must match.

!~

Substring must not match.

=

The full string must match.

<>

The full string must not match.

==

The numerical value must match.

!=

The numerical value must not match.

<=

The numerical value of the field must be LE than the value.

<

The numerical value of the field must be LT than the value.

>=

The numerical value of the field must be GT than the value.

>=

The numerical value of the field must be GE than the value.

-n

True if value is not empty (no value allowed).

-z

True if value is empty (no value allowed).

-t

Alias for "PROPNAME != 0" (no value allowed).

-f

Alias for "PROPNAME == 0" (no value allowed).

Values for flag must be space separated. The supported flags are:

–

VALUE spans to the end of the expression.

-c

The string match in this part is done case-sensitive.

The filter options concatenate several specifications for a filter of the same type. For example the four options in this example:

 --import-option keep-uid="uid =~ Alfa"
 --import-option keep-uid="&& uid !~ Test"
 --import-option keep-uid="|| uid =~ Alpha"
 --import-option keep-uid="uid !~ Test"

which is equivalent to

 --import-option \
  keep-uid="uid =~ Alfa" && uid !~ Test" || uid =~ Alpha" && "uid !~ Test"

imports only the user ids of a key containing the strings "Alfa" or "Alpha" but not the string "test".

RETURN VALUE

The program returns 0 if everything was fine, 1 if at least a signature was bad, and other error codes for fatal errors.

WARNINGS

Use a *good* password for your user account and a *good* passphrase to protect your secret key. This passphrase is the weakest part of the whole system. Programs to do dictionary attacks on your secret keyring are very easy to write and so you should protect your "~/.gnupg/" directory very well.

Keep in mind that, if this program is used over a network (telnet), it is *very* easy to spy out your passphrase!

If you are going to verify detached signatures, make sure that the program knows about it; either give both filenames on the command line or use ‘-’ to specify STDIN.

INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS

GnuPG tries to be a very flexible implementation of the OpenPGP standard. In particular, GnuPG implements many of the optional parts of the standard, such as the SHA-512 hash, and the ZLIB and BZIP2 compression algorithms. It is important to be aware that not all OpenPGP programs implement these optional algorithms and that by forcing their use via the --cipher-algo, --digest-algo, --cert-digest-algo, or --compress-algo options in GnuPG, it is possible to create a perfectly valid OpenPGP message, but one that cannot be read by the intended recipient.

There are dozens of variations of OpenPGP programs available, and each supports a slightly different subset of these optional algorithms. For example, until recently, no (unhacked) version of PGP supported the BLOWFISH cipher algorithm. A message using BLOWFISH simply could not be read by a PGP user. By default, GnuPG uses the standard OpenPGP preferences system that will always do the right thing and create messages that are usable by all recipients, regardless of which OpenPGP program they use. Only override this safe default if you really know what you are doing.

If you absolutely must override the safe default, or if the preferences on a given key are invalid for some reason, you are far better off using the --pgp6, --pgp7, or --pgp8 options. These options are safe as they do not force any particular algorithms in violation of OpenPGP, but rather reduce the available algorithms to a "PGP-safe" list.

BUGS

On older systems this program should be installed as setuid(root). This is necessary to lock memory pages. Locking memory pages prevents the operating system from writing memory pages (which may contain passphrases or other sensitive material) to disk. If you get no warning message about insecure memory your operating system supports locking without being root. The program drops root privileges as soon as locked memory is allocated.

Note also that some systems (especially laptops) have the ability to “suspend to disk” (also known as “safe sleep” or “hibernate”). This writes all memory to disk before going into a low power or even powered off mode. Unless measures are taken in the operating system to protect the saved memory, passphrases or other sensitive material may be recoverable from it later.

Before you report a bug you should first search the mailing list archives for similar problems and second check whether such a bug has already been reported to our bug tracker at http://bugs.gnupg.org .

4.5 Unattended Usage

gpg is often used as a backend engine by other software. To help with this a machine interface has been defined to have an unambiguous way to do this. The options --status-fd and --batch are almost always required for this.

4.5.1 Unattended key generation

The command --gen-key may be used along with the option --batch for unattended key generation. The parameters are either read from stdin or given as a file on the command line. The format of the parameter file is as follows:

• Text only, line length is limited to about 1000 characters.
• UTF-8 encoding must be used to specify non-ASCII characters.
• Empty lines are ignored.
• Leading and trailing while space is ignored.
• A hash sign as the first non white space character indicates a comment line.
• Control statements are indicated by a leading percent sign, the arguments are separated by white space from the keyword.
• Parameters are specified by a keyword, followed by a colon. Arguments are separated by white space.
• The first parameter must be ‘Key-Type’; control statements may be placed anywhere.
• The order of the parameters does not matter except for ‘Key-Type’ which must be the first parameter. The parameters are only used for the generated keyblock (primary and subkeys); parameters from previous sets are not used. Some syntactically checks may be performed.
• Key generation takes place when either the end of the parameter file is reached, the next ‘Key-Type’ parameter is encountered or at the control statement ‘%commit’ is encountered.

Control statements:

%echo text

Print text as diagnostic.

%dry-run

Suppress actual key generation (useful for syntax checking).

%commit

Perform the key generation. Note that an implicit commit is done at the next Key-Type parameter.

%pubring filename

%secring filename

Do not write the key to the default or commandline given keyring but to filename. This must be given before the first commit to take place, duplicate specification of the same filename is ignored, the last filename before a commit is used. The filename is used until a new filename is used (at commit points) and all keys are written to that file. If a new filename is given, this file is created (and overwrites an existing one). For GnuPG versions prior to 2.1, both control statements must be given. For GnuPG 2.1 and later ‘%secring’ is a no-op.

%ask-passphrase

%no-ask-passphrase

This option is a no-op for GnuPG 2.1 and later.

%no-protection

Using this option allows the creation of keys without any passphrase protection. This option is mainly intended for regression tests.

%transient-key

If given the keys are created using a faster and a somewhat less secure random number generator. This option may be used for keys which are only used for a short time and do not require full cryptographic strength. It takes only effect if used together with the control statement ‘%no-protection’.

General Parameters:

Key-Type: algo

Starts a new parameter block by giving the type of the primary key. The algorithm must be capable of signing. This is a required parameter. algo may either be an OpenPGP algorithm number or a string with the algorithm name. The special value ‘default’ may be used for algo to create the default key type; in this case a ‘Key-Usage’ shall not be given and ‘default’ also be used for ‘Subkey-Type’.

Key-Length: nbits

The requested length of the generated key in bits. The default is returned by running the command ‘gpg2 --gpgconf-list’.

Key-Grip: hexstring

This is optional and used to generate a CSR or certificate for an already existing key. Key-Length will be ignored when given.

Key-Usage: usage-list

Space or comma delimited list of key usages. Allowed values are ‘encrypt’, ‘sign’, and ‘auth’. This is used to generate the key flags. Please make sure that the algorithm is capable of this usage. Note that OpenPGP requires that all primary keys are capable of certification, so no matter what usage is given here, the ‘cert’ flag will be on. If no ‘Key-Usage’ is specified and the ‘Key-Type’ is not ‘default’, all allowed usages for that particular algorithm are used; if it is not given but ‘default’ is used the usage will be ‘sign’.

Subkey-Type: algo

This generates a secondary key (subkey). Currently only one subkey can be handled. See also ‘Key-Type’ above.

Subkey-Length: nbits

Length of the secondary key (subkey) in bits. The default is returned by running the command ‘gpg2 --gpgconf-list’".

Subkey-Usage: usage-list

Key usage lists for a subkey; similar to ‘Key-Usage’.

Passphrase: string

If you want to specify a passphrase for the secret key, enter it here. Default is to use the Pinentry dialog to ask for a passphrase.

Name-Real: name

Name-Comment: comment

Name-Email: email

The three parts of a user name. Remember to use UTF-8 encoding here. If you don’t give any of them, no user ID is created.

Expire-Date: iso-date|(number[d|w|m|y])

Set the expiration date for the key (and the subkey). It may either be entered in ISO date format (e.g. "20000815T145012") or as number of days, weeks, month or years after the creation date. The special notation "seconds=N" is also allowed to specify a number of seconds since creation. Without a letter days are assumed. Note that there is no check done on the overflow of the type used by OpenPGP for timestamps. Thus you better make sure that the given value make sense. Although OpenPGP works with time intervals, GnuPG uses an absolute value internally and thus the last year we can represent is 2105.

Creation-Date: iso-date

Set the creation date of the key as stored in the key information and which is also part of the fingerprint calculation. Either a date like "1986-04-26" or a full timestamp like "19860426T042640" may be used. The time is considered to be UTC. The special notation "seconds=N" may be used to directly specify a the number of seconds since Epoch (Unix time). If it is not given the current time is used.

Preferences: string

Set the cipher, hash, and compression preference values for this key. This expects the same type of string as the sub-command ‘setpref’ in the --edit-key menu.

Revoker: algo:fpr [sensitive]

Add a designated revoker to the generated key. Algo is the public key algorithm of the designated revoker (i.e. RSA=1, DSA=17, etc.) fpr is the fingerprint of the designated revoker. The optional ‘sensitive’ flag marks the designated revoker as sensitive information. Only v4 keys may be designated revokers.

Keyserver: string

This is an optional parameter that specifies the preferred keyserver URL for the key.

Handle: string

This is an optional parameter only used with the status lines KEY_CREATED and KEY_NOT_CREATED. string may be up to 100 characters and should not contain spaces. It is useful for batch key generation to associate a key parameter block with a status line.

Here is an example on how to create a key:

$ cat >foo <<EOF
     %echo Generating a basic OpenPGP key
     Key-Type: DSA
     Key-Length: 1024
     Subkey-Type: ELG-E
     Subkey-Length: 1024
     Name-Real: Joe Tester
     Name-Comment: with stupid passphrase
     Name-Email: joe@foo.bar
     Expire-Date: 0
     Passphrase: abc
     %pubring foo.pub
     %secring foo.sec
     # Do a commit here, so that we can later print "done" :-)
     %commit
     %echo done
EOF
$ gpg2 --batch --gen-key foo
 [...]
$ gpg2 --no-default-keyring --secret-keyring ./foo.sec \
       --keyring ./foo.pub --list-secret-keys
/home/wk/work/gnupg-stable/scratch/foo.sec
------------------------------------------
sec  1024D/915A878D 2000-03-09 Joe Tester (with stupid passphrase) <joe@foo.bar>
ssb  1024g/8F70E2C0 2000-03-09

If you want to create a key with the default algorithms you would use these parameters:

     %echo Generating a default key
     Key-Type: default
     Subkey-Type: default
     Name-Real: Joe Tester
     Name-Comment: with stupid passphrase
     Name-Email: joe@foo.bar
     Expire-Date: 0
     Passphrase: abc
     %pubring foo.pub
     %secring foo.sec
     # Do a commit here, so that we can later print "done" :-)
     %commit
     %echo done

5 Invoking GPGSM

gpgsm is a tool similar to gpg to provide digital encryption and signing services on X.509 certificates and the CMS protocol. It is mainly used as a backend for S/MIME mail processing. gpgsm includes a full featured certificate management and complies with all rules defined for the German Sphinx project.

See Option Index, for an index to GPGSM’s commands and options.

Developer information:

5.1 Commands

Commands are not distinguished from options except for the fact that only one command is allowed.

5.1.1 Commands not specific to the function

--version

Print the program version and licensing information. Note that you cannot abbreviate this command.

--help, -h

Print a usage message summarizing the most useful command-line options. Note that you cannot abbreviate this command.

--warranty

Print warranty information. Note that you cannot abbreviate this command.

--dump-options

Print a list of all available options and commands. Note that you cannot abbreviate this command.

5.1.2 Commands to select the type of operation

--encrypt

Perform an encryption. The keys the data is encrypted too must be set using the option --recipient.

--decrypt

Perform a decryption; the type of input is automatically determined. It may either be in binary form or PEM encoded; automatic determination of base-64 encoding is not done.

--sign

Create a digital signature. The key used is either the fist one found in the keybox or those set with the --local-user option.

--verify

Check a signature file for validity. Depending on the arguments a detached signature may also be checked.

--server

Run in server mode and wait for commands on the stdin.

--call-dirmngr command [args]

Behave as a Dirmngr client issuing the request command with the optional list of args. The output of the Dirmngr is printed stdout. Please note that file names given as arguments should have an absolute file name (i.e. commencing with / because they are passed verbatim to the Dirmngr and the working directory of the Dirmngr might not be the same as the one of this client. Currently it is not possible to pass data via stdin to the Dirmngr. command should not contain spaces.

This is command is required for certain maintaining tasks of the dirmngr where a dirmngr must be able to call back to gpgsm. See the Dirmngr manual for details.

--call-protect-tool arguments

Certain maintenance operations are done by an external program call gpg-protect-tool; this is usually not installed in a directory listed in the PATH variable. This command provides a simple wrapper to access this tool. arguments are passed verbatim to this command; use ‘--help’ to get a list of supported operations.

5.1.3 How to manage the certificates and keys

--gen-key

This command allows the creation of a certificate signing request or a self-signed certificate. It is commonly used along with the --output option to save the created CSR or certificate into a file. If used with the --batch a parameter file is used to create the CSR or certificate and it is further possible to create non-self-signed certificates.

--list-keys

-k

List all available certificates stored in the local key database. Note that the displayed data might be reformatted for better human readability and illegal characters are replaced by safe substitutes.

--list-secret-keys

-K

List all available certificates for which a corresponding a secret key is available.

--list-external-keys pattern

List certificates matching pattern using an external server. This utilizes the dirmngr service.

--list-chain

Same as --list-keys but also prints all keys making up the chain.

--dump-cert

--dump-keys

List all available certificates stored in the local key database using a format useful mainly for debugging.

--dump-chain

Same as --dump-keys but also prints all keys making up the chain.

--dump-secret-keys

List all available certificates for which a corresponding a secret key is available using a format useful mainly for debugging.

--dump-external-keys pattern

List certificates matching pattern using an external server. This utilizes the dirmngr service. It uses a format useful mainly for debugging.

--keydb-clear-some-cert-flags

This is a debugging aid to reset certain flags in the key database which are used to cache certain certificate stati. It is especially useful if a bad CRL or a weird running OCSP responder did accidentally revoke certificate. There is no security issue with this command because gpgsm always make sure that the validity of a certificate is checked right before it is used.

--delete-keys pattern

Delete the keys matching pattern. Note that there is no command to delete the secret part of the key directly. In case you need to do this, you should run the command gpgsm --dump-secret-keys KEYID before you delete the key, copy the string of hex-digits in the “keygrip” line and delete the file consisting of these hex-digits and the suffix .key from the private-keys-v1.d directory below our GnuPG home directory (usually ~/.gnupg).

--export [pattern]

Export all certificates stored in the Keybox or those specified by the optional pattern. Those pattern consist of a list of user ids (see how-to-specify-a-user-id). When used along with the --armor option a few informational lines are prepended before each block. There is one limitation: As there is no commonly agreed upon way to pack more than one certificate into an ASN.1 structure, the binary export (i.e. without using armor) works only for the export of one certificate. Thus it is required to specify a pattern which yields exactly one certificate. Ephemeral certificate are only exported if all pattern are given as fingerprints or keygrips.

--export-secret-key-p12 key-id

Export the private key and the certificate identified by key-id in a PKCS#12 format. When used with the --armor option a few informational lines are prepended to the output. Note, that the PKCS#12 format is not very secure and this command is only provided if there is no other way to exchange the private key. (see option --p12-charset)

--export-secret-key-p8 key-id

--export-secret-key-raw key-id

Export the private key of the certificate identified by key-id with any encryption stripped. The ...-raw command exports in PKCS#1 format; the ...-p8 command exports in PKCS#8 format. When used with the --armor option a few informational lines are prepended to the output. These commands are useful to prepare a key for use on a TLS server.

--import [files]

Import the certificates from the PEM or binary encoded files as well as from signed-only messages. This command may also be used to import a secret key from a PKCS#12 file.

--learn-card

Read information about the private keys from the smartcard and import the certificates from there. This command utilizes the gpg-agent and in turn the scdaemon.

--passwd user_id

Change the passphrase of the private key belonging to the certificate specified as user_id. Note, that changing the passphrase/PIN of a smartcard is not yet supported.

5.2 Option Summary

GPGSM features a bunch of options to control the exact behaviour and to change the default configuration.

5.2.1 How to change the configuration

These options are used to change the configuration and are usually found in the option file.

--options file

Reads configuration from file instead of from the default per-user configuration file. The default configuration file is named gpgsm.conf and expected in the .gnupg directory directly below the home directory of the user.

--homedir dir

Set the name of the home directory to dir. If this option is not used, the home directory defaults to ~/.gnupg. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable GNUPGHOME or (on Windows systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

On Windows systems it is possible to install GnuPG as a portable application. In this case only this command line option is considered, all other ways to set a home directory are ignored.

To install GnuPG as a portable application under Windows, create an empty file name gpgconf.ctl in the same directory as the tool gpgconf.exe. The root of the installation is than that directory; or, if gpgconf.exe has been installed directly below a directory named bin, its parent directory. You also need to make sure that the following directories exist and are writable: ROOT/home for the GnuPG home and ROOT/usr/var/cache/gnupg for internal cache files.

-v

--verbose

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to gpgsm, such as ‘-vv’.

--policy-file filename

Change the default name of the policy file to filename.

--agent-program file

Specify an agent program to be used for secret key operations. The default value is determined by running the command gpgconf. Note that the pipe symbol (|) is used for a regression test suite hack and may thus not be used in the file name.

--dirmngr-program file

Specify a dirmngr program to be used for CRL checks. The default value is /usr/bin/dirmngr.

--prefer-system-dirmngr

If a system wide dirmngr is running in daemon mode, first try to connect to this one. Fallback to a pipe based server if this does not work. Under Windows this option is ignored because the system dirmngr is always used.

--disable-dirmngr

Entirely disable the use of the Dirmngr.

--no-autostart

Do not start the gpg-agent or the dirmngr if it has not yet been started and its service is required. This option is mostly useful on machines where the connection to gpg-agent has been redirected to another machines. If dirmngr is required on the remote machine, it may be started manually using gpgconf --launch dirmngr.

--no-secmem-warning

Do not print a warning when the so called "secure memory" cannot be used.

--log-file file

When running in server mode, append all logging output to file.

5.2.2 Certificate related options

--enable-policy-checks

--disable-policy-checks

By default policy checks are enabled. These options may be used to change it.

--enable-crl-checks

--disable-crl-checks

By default the CRL checks are enabled and the DirMngr is used to check for revoked certificates. The disable option is most useful with an off-line network connection to suppress this check.

--enable-trusted-cert-crl-check

--disable-trusted-cert-crl-check

By default the CRL for trusted root certificates are checked like for any other certificates. This allows a CA to revoke its own certificates voluntary without the need of putting all ever issued certificates into a CRL. The disable option may be used to switch this extra check off. Due to the caching done by the Dirmngr, there will not be any noticeable performance gain. Note, that this also disables possible OCSP checks for trusted root certificates. A more specific way of disabling this check is by adding the “relax” keyword to the root CA line of the trustlist.txt

--force-crl-refresh

Tell the dirmngr to reload the CRL for each request. For better performance, the dirmngr will actually optimize this by suppressing the loading for short time intervals (e.g. 30 minutes). This option is useful to make sure that a fresh CRL is available for certificates hold in the keybox. The suggested way of doing this is by using it along with the option --with-validation for a key listing command. This option should not be used in a configuration file.

--enable-ocsp

--disable-ocsp

By default OCSP checks are disabled. The enable option may be used to enable OCSP checks via Dirmngr. If CRL checks are also enabled, CRLs will be used as a fallback if for some reason an OCSP request will not succeed. Note, that you have to allow OCSP requests in Dirmngr’s configuration too (option --allow-ocsp) and configure Dirmngr properly. If you do not do so you will get the error code ‘Not supported’.

--auto-issuer-key-retrieve

If a required certificate is missing while validating the chain of certificates, try to load that certificate from an external location. This usually means that Dirmngr is employed to search for the certificate. Note that this option makes a "web bug" like behavior possible. LDAP server operators can see which keys you request, so by sending you a message signed by a brand new key (which you naturally will not have on your local keybox), the operator can tell both your IP address and the time when you verified the signature.

--validation-model name

This option changes the default validation model. The only possible values are "shell" (which is the default), "chain" which forces the use of the chain model and "steed" for a new simplified model. The chain model is also used if an option in the trustlist.txt or an attribute of the certificate requests it. However the standard model (shell) is in that case always tried first.

--ignore-cert-extension oid

Add oid to the list of ignored certificate extensions. The oid is expected to be in dotted decimal form, like 2.5.29.3. This option may be used more than once. Critical flagged certificate extensions matching one of the OIDs in the list are treated as if they are actually handled and thus the certificate will not be rejected due to an unknown critical extension. Use this option with care because extensions are usually flagged as critical for a reason.

5.2.3 Input and Output

--armor

-a

Create PEM encoded output. Default is binary output.

--base64

Create Base-64 encoded output; i.e. PEM without the header lines.

--assume-armor

Assume the input data is PEM encoded. Default is to autodetect the encoding but this is may fail.

--assume-base64

Assume the input data is plain base-64 encoded.

--assume-binary

Assume the input data is binary encoded.

--p12-charset name

gpgsm uses the UTF-8 encoding when encoding passphrases for PKCS#12 files. This option may be used to force the passphrase to be encoded in the specified encoding name. This is useful if the application used to import the key uses a different encoding and thus will not be able to import a file generated by gpgsm. Commonly used values for name are Latin1 and CP850. Note that gpgsm itself automagically imports any file with a passphrase encoded to the most commonly used encodings.

--default-key user_id

Use user_id as the standard key for signing. This key is used if no other key has been defined as a signing key. Note, that the first --local-users option also sets this key if it has not yet been set; however --default-key always overrides this.

--local-user user_id

-u user_id

Set the user(s) to be used for signing. The default is the first secret key found in the database.

--recipient name

-r

Encrypt to the user id name. There are several ways a user id may be given (see how-to-specify-a-user-id).

--output file

-o file

Write output to file. The default is to write it to stdout.

--with-key-data

Displays extra information with the --list-keys commands. Especially a line tagged grp is printed which tells you the keygrip of a key. This string is for example used as the file name of the secret key.

--with-validation

When doing a key listing, do a full validation check for each key and print the result. This is usually a slow operation because it requires a CRL lookup and other operations.

When used along with –import, a validation of the certificate to import is done and only imported if it succeeds the test. Note that this does not affect an already available certificate in the DB. This option is therefore useful to simply verify a certificate.

--with-md5-fingerprint

For standard key listings, also print the MD5 fingerprint of the certificate.

--with-keygrip

Include the keygrip in standard key listings. Note that the keygrip is always listed in –with-colons mode.

--with-secret

Include info about the presence of a secret key in public key listings done with --with-colons.

5.2.4 How to change how the CMS is created.

--include-certs n

Using n of -2 includes all certificate except for the root cert, -1 includes all certs, 0 does not include any certs, 1 includes only the signers cert and all other positive values include up to n certificates starting with the signer cert. The default is -2.

--cipher-algo oid

Use the cipher algorithm with the ASN.1 object identifier oid for encryption. For convenience the strings 3DES, AES and AES256 may be used instead of their OIDs. The default is AES (2.16.840.1.101.3.4.1.2).

--digest-algo name

Use name as the message digest algorithm. Usually this algorithm is deduced from the respective signing certificate. This option forces the use of the given algorithm and may lead to severe interoperability problems.

5.2.5 Doing things one usually do not want to do.

--extra-digest-algo name

Sometimes signatures are broken in that they announce a different digest algorithm than actually used. gpgsm uses a one-pass data processing model and thus needs to rely on the announced digest algorithms to properly hash the data. As a workaround this option may be used to tell gpg to also hash the data using the algorithm name; this slows processing down a little bit but allows verification of such broken signatures. If gpgsm prints an error like “digest algo 8 has not been enabled” you may want to try this option, with ‘SHA256’ for name.

--faked-system-time epoch

This option is only useful for testing; it sets the system time back or forth to epoch which is the number of seconds elapsed since the year 1970. Alternatively epoch may be given as a full ISO time string (e.g. "20070924T154812").

--with-ephemeral-keys

Include ephemeral flagged keys in the output of key listings. Note that they are included anyway if the key specification for a listing is given as fingerprint or keygrip.

--debug-level level

Select the debug level for investigating problems. level may be a numeric value or by a keyword:

none

No debugging at all. A value of less than 1 may be used instead of the keyword.

basic

Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

advanced

More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

expert

Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

guru

All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

--debug flags

This option is only useful for debugging and the behaviour may change at any time without notice; using --debug-levels is the preferred method to select the debug verbosity. FLAGS are bit encoded and may be given in usual C-Syntax. The currently defined bits are:

0 (1)

X.509 or OpenPGP protocol related data

1 (2)

values of big number integers

2 (4)

low level crypto operations

5 (32)

memory allocation

6 (64)

caching

7 (128)

show memory statistics.

9 (512)

write hashed data to files named dbgmd-000*

10 (1024)

trace Assuan protocol

Note, that all flags set using this option may get overridden by --debug-level.

--debug-all

Same as --debug=0xffffffff

--debug-allow-core-dump

Usually gpgsm tries to avoid dumping core by well written code and by disabling core dumps for security reasons. However, bugs are pretty durable beasts and to squash them it is sometimes useful to have a core dump. This option enables core dumps unless the Bad Thing happened before the option parsing.

--debug-no-chain-validation

This is actually not a debugging option but only useful as such. It lets gpgsm bypass all certificate chain validation checks.

--debug-ignore-expiration

This is actually not a debugging option but only useful as such. It lets gpgsm ignore all notAfter dates, this is used by the regression tests.

--passphrase-fd n

Read the passphrase from file descriptor n. Only the first line will be read from file descriptor n. If you use 0 for n, the passphrase will be read from STDIN. This can only be used if only one passphrase is supplied.

Note that this passphrase is only used if the option --batch has also been given.

--pinentry-mode mode

Set the pinentry mode to mode. Allowed values for mode are:

default

Use the default of the agent, which is ask.

ask

Force the use of the Pinentry.

cancel

Emulate use of Pinentry’s cancel button.

error

Return a Pinentry error (“No Pinentry”).

loopback

Redirect Pinentry queries to the caller. Note that in contrast to Pinentry the user is not prompted again if he enters a bad password.

--no-common-certs-import

Suppress the import of common certificates on keybox creation.

All the long options may also be given in the configuration file after stripping off the two leading dashes.

5.3 Configuration files

There are a few configuration files to control certain aspects of gpgsm’s operation. Unless noted, they are expected in the current home directory (see option --homedir).

gpgsm.conf

This is the standard configuration file read by gpgsm on startup. It may contain any valid long option; the leading two dashes may not be entered and the option may not be abbreviated. This default name may be changed on the command line (see gpgsm-option --options). You should backup this file.

policies.txt

This is a list of allowed CA policies. This file should list the object identifiers of the policies line by line. Empty lines and lines starting with a hash mark are ignored. Policies missing in this file and not marked as critical in the certificate will print only a warning; certificates with policies marked as critical and not listed in this file will fail the signature verification. You should backup this file.

For example, to allow only the policy 2.289.9.9, the file should look like this:

# Allowed policies
2.289.9.9

qualified.txt

This is the list of root certificates used for qualified certificates. They are defined as certificates capable of creating legally binding signatures in the same way as handwritten signatures are. Comments start with a hash mark and empty lines are ignored. Lines do have a length limit but this is not a serious limitation as the format of the entries is fixed and checked by gpgsm: A non-comment line starts with optional whitespace, followed by exactly 40 hex character, white space and a lowercased 2 letter country code. Additional data delimited with by a white space is current ignored but might late be used for other purposes.

Note that even if a certificate is listed in this file, this does not mean that the certificate is trusted; in general the certificates listed in this file need to be listed also in trustlist.txt.

This is a global file an installed in the data directory (e.g. /usr/share/gnupg/qualified.txt). GnuPG installs a suitable file with root certificates as used in Germany. As new Root-CA certificates may be issued over time, these entries may need to be updated; new distributions of this software should come with an updated list but it is still the responsibility of the Administrator to check that this list is correct.

Everytime gpgsm uses a certificate for signing or verification this file will be consulted to check whether the certificate under question has ultimately been issued by one of these CAs. If this is the case the user will be informed that the verified signature represents a legally binding (“qualified”) signature. When creating a signature using such a certificate an extra prompt will be issued to let the user confirm that such a legally binding signature shall really be created.

Because this software has not yet been approved for use with such certificates, appropriate notices will be shown to indicate this fact.

help.txt

This is plain text file with a few help entries used with pinentry as well as a large list of help items for gpg and gpgsm. The standard file has English help texts; to install localized versions use filenames like help.LL.txt with LL denoting the locale. GnuPG comes with a set of predefined help files in the data directory (e.g. /usr/share/gnupg/gnupg/help.de.txt) and allows overriding of any help item by help files stored in the system configuration directory (e.g. /usr/etc/gnupg/help.de.txt). For a reference of the help file’s syntax, please see the installed help.txt file.

com-certs.pem

This file is a collection of common certificates used to populated a newly created pubring.kbx. An administrator may replace this file with a custom one. The format is a concatenation of PEM encoded X.509 certificates. This global file is installed in the data directory (e.g. /usr/share/gnupg/com-certs.pem).

Note that on larger installations, it is useful to put predefined files into the directory /etc/skel/.gnupg/ so that newly created users start up with a working configuration. For existing users a small helper script is provided to create these files (see addgnupghome).

For internal purposes gpgsm creates and maintains a few other files; they all live in in the current home directory (see option --homedir). Only gpgsm may modify these files.

pubring.kbx

This a database file storing the certificates as well as meta information. For debugging purposes the tool kbxutil may be used to show the internal structure of this file. You should backup this file.

random_seed

This content of this file is used to maintain the internal state of the random number generator across invocations. The same file is used by other programs of this software too.

S.gpg-agent

If this file exists gpgsm will first try to connect to this socket for accessing gpg-agent before starting a new gpg-agent instance. Under Windows this socket (which in reality be a plain file describing a regular TCP listening port) is the standard way of connecting the gpg-agent.

5.4 Examples

$ gpgsm -er goo@bar.net <plaintext >ciphertext

5.5 Unattended Usage

gpgsm is often used as a backend engine by other software. To help with this a machine interface has been defined to have an unambiguous way to do this. This is most likely used with the --server command but may also be used in the standard operation mode by using the --status-fd option.

5.5.1 Automated signature checking

It is very important to understand the semantics used with signature verification. Checking a signature is not as simple as it may sound and so the operation is a bit complicated. In most cases it is required to look at several status lines. Here is a table of all cases a signed message may have:

The signature is valid

This does mean that the signature has been successfully verified, the certificates are all sane. However there are two subcases with important information: One of the certificates may have expired or a signature of a message itself as expired. It is a sound practise to consider such a signature still as valid but additional information should be displayed. Depending on the subcase gpgsm will issue these status codes:

signature valid and nothing did expire

GOODSIG, VALIDSIG, TRUST_FULLY

signature valid but at least one certificate has expired

EXPKEYSIG, VALIDSIG, TRUST_FULLY

signature valid but expired

EXPSIG, VALIDSIG, TRUST_FULLY Note, that this case is currently not implemented.

The signature is invalid

This means that the signature verification failed (this is an indication of af a transfer error, a program error or tampering with the message). gpgsm issues one of these status codes sequences:

BADSIG

GOODSIG, VALIDSIG TRUST_NEVER

Error verifying a signature

For some reason the signature could not be verified, i.e. it cannot be decided whether the signature is valid or invalid. A common reason for this is a missing certificate.

5.5.2 CSR and certificate creation

The command --gen-key may be used along with the option --batch to either create a certificate signing request (CSR) or an X.509 certificate. This is controlled by a parameter file; the format of this file is as follows:

• Text only, line length is limited to about 1000 characters.
• UTF-8 encoding must be used to specify non-ASCII characters.
• Empty lines are ignored.
• Leading and trailing while space is ignored.
• A hash sign as the first non white space character indicates a comment line.
• Control statements are indicated by a leading percent sign, the arguments are separated by white space from the keyword.
• Parameters are specified by a keyword, followed by a colon. Arguments are separated by white space.
• The first parameter must be ‘Key-Type’, control statements may be placed anywhere.
• The order of the parameters does not matter except for ‘Key-Type’ which must be the first parameter. The parameters are only used for the generated CSR/certificate; parameters from previous sets are not used. Some syntactically checks may be performed.
• Key generation takes place when either the end of the parameter file is reached, the next ‘Key-Type’ parameter is encountered or at the control statement ‘%commit’ is encountered.

Control statements:

%echo text

Print text as diagnostic.

%dry-run

Suppress actual key generation (useful for syntax checking).

%commit

Perform the key generation. Note that an implicit commit is done at the next Key-Type parameter.

General Parameters:

Key-Type: algo

Starts a new parameter block by giving the type of the primary key. The algorithm must be capable of signing. This is a required parameter. The only supported value for algo is ‘rsa’.

Key-Length: nbits

The requested length of a generated key in bits. Defaults to 2048.

Key-Grip: hexstring

This is optional and used to generate a CSR or certificatet for an already existing key. Key-Length will be ignored when given.

Key-Usage: usage-list

Space or comma delimited list of key usage, allowed values are ‘encrypt’, ‘sign’ and ‘cert’. This is used to generate the keyUsage extension. Please make sure that the algorithm is capable of this usage. Default is to allow encrypt and sign.

Name-DN: subject-name

This is the Distinguished Name (DN) of the subject in RFC-2253 format.

Name-Email: string

This is an email address for the altSubjectName. This parameter is optional but may occur several times to add several email addresses to a certificate.

Name-DNS: string

The is an DNS name for the altSubjectName. This parameter is optional but may occur several times to add several DNS names to a certificate.

Name-URI: string

This is an URI for the altSubjectName. This parameter is optional but may occur several times to add several URIs to a certificate.

Additional parameters used to create a certificate (in contrast to a certificate signing request):

Serial: sn

If this parameter is given an X.509 certificate will be generated. sn is expected to be a hex string representing an unsigned integer of arbitary length. The special value ‘random’ can be used to create a 64 bit random serial number.

Issuer-DN: issuer-name

This is the DN name of the issuer in rfc2253 format. If it is not set it will default to the subject DN and a special GnuPG extension will be included in the certificate to mark it as a standalone certificate.

Creation-Date: iso-date

Not-Before: iso-date

Set the notBefore date of the certificate. Either a date like ‘1986-04-26’ or ‘1986-04-26 12:00’ or a standard ISO timestamp like ‘19860426T042640’ may be used. The time is considered to be UTC. If it is not given the current date is used.

Expire-Date: iso-date

Not-After: iso-date

Set the notAfter date of the certificate. Either a date like ‘2063-04-05’ or ‘2063-04-05 17:00’ or a standard ISO timestamp like ‘20630405T170000’ may be used. The time is considered to be UTC. If it is not given a default value in the not too far future is used.

Signing-Key: keygrip

This gives the keygrip of the key used to sign the certificate. If it is not given a self-signed certificate will be created. For compatibility with future versions, it is suggested to prefix the keygrip with a ‘&’.

Hash-Algo: hash-algo

Use hash-algo for this CSR or certificate. The supported hash algorithms are: ‘sha1’, ‘sha256’, ‘sha384’ and ‘sha512’; they may also be specified with uppercase letters. The default is ‘sha256’.

5.6 The Protocol the Server Mode Uses.

Description of the protocol used to access GPGSM. GPGSM does implement the Assuan protocol and in addition provides a regular command line interface which exhibits a full client to this protocol (but uses internal linking). To start gpgsm as a server the command line the option --server must be used. Additional options are provided to select the communication method (i.e. the name of the socket).

We assume that the connection has already been established; see the Assuan manual for details.

5.6.1 Encrypting a Message

Before encryption can be done the recipient must be set using the command:

  RECIPIENT userID

Set the recipient for the encryption. userID should be the internal representation of the key; the server may accept any other way of specification. If this is a valid and trusted recipient the server does respond with OK, otherwise the return is an ERR with the reason why the recipient cannot be used, the encryption will then not be done for this recipient. If the policy is not to encrypt at all if not all recipients are valid, the client has to take care of this. All RECIPIENT commands are cumulative until a RESET or an successful ENCRYPT command.

  INPUT FD[=n] [--armor|--base64|--binary]

Set the file descriptor for the message to be encrypted to n. Obviously the pipe must be open at that point, the server establishes its own end. If the server returns an error the client should consider this session failed. If n is not given, this commands uses the last file descriptor passed to the application. See the assuan_sendfd function in the Libassuan manual, on how to do descriptor passing.

The --armor option may be used to advice the server that the input data is in PEM format, --base64 advices that a raw base-64 encoding is used, --binary advices of raw binary input (BER). If none of these options is used, the server tries to figure out the used encoding, but this may not always be correct.

  OUTPUT FD[=n] [--armor|--base64]

Set the file descriptor to be used for the output (i.e. the encrypted message). Obviously the pipe must be open at that point, the server establishes its own end. If the server returns an error he client should consider this session failed.

The option armor encodes the output in PEM format, the --base64 option applies just a base 64 encoding. No option creates binary output (BER).

The actual encryption is done using the command

  ENCRYPT

It takes the plaintext from the INPUT command, writes to the ciphertext to the file descriptor set with the OUTPUT command, take the recipients from all the recipients set so far. If this command fails the clients should try to delete all output currently done or otherwise mark it as invalid. GPGSM does ensure that there will not be any security problem with leftover data on the output in this case.

This command should in general not fail, as all necessary checks have been done while setting the recipients. The input and output pipes are closed.

5.6.2 Decrypting a message

Input and output FDs are set the same way as in encryption, but INPUT refers to the ciphertext and output to the plaintext. There is no need to set recipients. GPGSM automatically strips any S/MIME headers from the input, so it is valid to pass an entire MIME part to the INPUT pipe.

The encryption is done by using the command

  DECRYPT

It performs the decrypt operation after doing some check on the internal state. (e.g. that all needed data has been set). Because it utilizes the GPG-Agent for the session key decryption, there is no need to ask the client for a protecting passphrase - GpgAgent takes care of this by requesting this from the user.

5.6.3 Signing a Message

Signing is usually done with these commands:

  INPUT FD[=n] [--armor|--base64|--binary]

This tells GPGSM to read the data to sign from file descriptor n.

  OUTPUT FD[=m] [--armor|--base64]

Write the output to file descriptor m. If a detached signature is requested, only the signature is written.

  SIGN [--detached]

Sign the data set with the INPUT command and write it to the sink set by OUTPUT. With --detached, a detached signature is created (surprise).

The key used for signing is the default one or the one specified in the configuration file. To get finer control over the keys, it is possible to use the command

  SIGNER userID

to the signer’s key. userID should be the internal representation of the key; the server may accept any other way of specification. If this is a valid and trusted recipient the server does respond with OK, otherwise the return is an ERR with the reason why the key cannot be used, the signature will then not be created using this key. If the policy is not to sign at all if not all keys are valid, the client has to take care of this. All SIGNER commands are cumulative until a RESET is done. Note that a SIGN does not reset this list of signers which is in contrats to the RECIPIENT command.

5.6.4 Verifying a Message

To verify a mesage the command:

  VERIFY

is used. It does a verify operation on the message send to the input FD. The result is written out using status lines. If an output FD was given, the signed text will be written to that. If the signature is a detached one, the server will inquire about the signed material and the client must provide it.

5.6.5 Generating a Key

This is used to generate a new keypair, store the secret part in the PSE and the public key in the key database. We will probably add optional commands to allow the client to select whether a hardware token is used to store the key. Configuration options to GPGSM can be used to restrict the use of this command.

  GENKEY

GPGSM checks whether this command is allowed and then does an INQUIRY to get the key parameters, the client should then send the key parameters in the native format:

    S: INQUIRE KEY_PARAM native
    C: D foo:fgfgfg
    C: D bar
    C: END

Please note that the server may send Status info lines while reading the data lines from the client. After this the key generation takes place and the server eventually does send an ERR or OK response. Status lines may be issued as a progress indicator.

5.6.6 List available keys

To list the keys in the internal database or using an external key provider, the command:

  LISTKEYS  pattern

is used. To allow multiple patterns (which are ORed during the search) quoting is required: Spaces are to be translated into "+" or into "%20"; in turn this requires that the usual escape quoting rules are done.

  LISTSECRETKEYS pattern

Lists only the keys where a secret key is available.

The list commands commands are affected by the option

  OPTION list-mode=mode

where mode may be:

0

Use default (which is usually the same as 1).

1

List only the internal keys.

2

List only the external keys.

3

List internal and external keys.

Note that options are valid for the entire session.

5.6.7 Export certificates

To export certificate from the internal key database the command:

  EXPORT [--data [--armor] [--base64]] [--] pattern

is used. To allow multiple patterns (which are ORed) quoting is required: Spaces are to be translated into "+" or into "%20"; in turn this requires that the usual escape quoting rules are done.

If the --data option has not been given, the format of the output depends on what was set with the OUTPUT command. When using PEM encoding a few informational lines are prepended.

If the --data has been given, a target set via OUTPUT is ignored and the data is returned inline using standard D-lines. This avoids the need for an extra file descriptor. In this case the options --armor and --base64 may be used in the same way as with the OUTPUT command.

5.6.8 Import certificates

To import certificates into the internal key database, the command

  IMPORT [--re-import]

is used. The data is expected on the file descriptor set with the INPUT command. Certain checks are performed on the certificate. Note that the code will also handle PKCS#12 files and import private keys; a helper program is used for that.

With the option --re-import the input data is expected to a be a linefeed separated list of fingerprints. The command will re-import the corresponding certificates; that is they are made permanent by removing their ephemeral flag.

5.6.9 Delete certificates

To delete a certificate the command

  DELKEYS pattern

is used. To allow multiple patterns (which are ORed) quoting is required: Spaces are to be translated into "+" or into "%20"; in turn this requires that the usual escape quoting rules are done.

The certificates must be specified unambiguously otherwise an error is returned.

5.6.10 Retrieve an audit log.

This command is used to retrieve an audit log.

GETAUDITLOG [--data] [--html]

If --data is used, the audit log is send using D-lines instead of being sent to the file descriptor given by an OUTPUT command. If --html is used, the output is formatted as an XHTML block. This is designed to be incorporated into a HTML document.

5.6.11 Return information about the process

This is a multipurpose function to return a variety of information.

GETINFO what

The value of what specifies the kind of information returned:

version

Return the version of the program.

pid

Return the process id of the process.

agent-check

Return OK if the agent is running.

cmd_has_option cmd opt

Return OK if the command cmd implements the option opt. The leading two dashes usually used with opt shall not be given.

offline

Return OK if the connection is in offline mode. This may be either due to a OPTION offline=1 or due to gpgsm being started with option --disable-dirmngr.

5.6.12 Session options.

The standard Assuan option handler supports these options.

OPTION name[=value]

These names are recognized:

putenv

Change the session’s environment to be passed via gpg-agent to Pinentry. value is a string of the form <KEY>[=[<STRING>]]. If only <KEY> is given the environment variable <KEY> is removed from the session environment, if <KEY>= is given that environment variable is set to the empty string, and if <STRING> is given it is set to that string.

display

Set the session environment variable DISPLAY is set to value.

ttyname

Set the session environment variable GPG_TTY is set to value.

ttytype

Set the session environment variable TERM is set to value.

lc-ctype

Set the session environment variable LC_CTYPE is set to value.

lc-messages

Set the session environment variable LC_MESSAGES is set to value.

xauthority

Set the session environment variable XAUTHORITY is set to value.

pinentry-user-data

Set the session environment variable PINENTRY_USER_DATA is set to value.

include-certs

This option overrides the command line option --include-certs. A value of -2 includes all certificates except for the root certificate, -1 includes all certicates, 0 does not include any certicates, 1 includes only the signers certicate and all other positive values include up to value certificates starting with the signer cert.

list-mode

See gpgsm-cmd listkeys.

list-to-output

If value is true the output of the list commands (see gpgsm-cmd listkeys) is written to the file descriptor set with the last OUTPUT command. If value is false the output is written via data lines; this is the default.

with-validation

If value is true for each listed certificate the validation status is printed. This may result in the download of a CRL or the user being asked about the trustworthiness of a root certificate. The default is given by a command line option (see gpgsm-option --with-validation).

with-secret

If value is true certificates with a corresponding private key are marked by the list commands.

validation-model

This option overrides the command line option validation-model for the session. (see gpgsm-option --validation-model.)

with-key-data

This option globally enables the command line option --with-key-data. (see gpgsm-option --with-key-data.)

enable-audit-log

If value is true data to write an audit log is gathered. (see gpgsm-cmd getauditlog.)

allow-pinentry-notify

If this option is used notifications about the launch of a Pinentry are passed back to the client.

with-ephemeral-keys

If value is true ephemeral certificates are included in the output of the list commands.

no-encrypt-to

If this option is used all keys set by the command line option --encrypt-to are ignored.

offline

If value is true or value is not given all network access is disabled for this session. This is the same as the command line option --disable-dirmngr.

6 Invoking the SCDAEMON

The scdaemon is a daemon to manage smartcards. It is usually invoked by gpg-agent and in general not used directly.

See Option Index, for an index to scdaemon’s commands and options.

6.1 Commands

Commands are not distinguished from options except for the fact that only one command is allowed.

--version

Print the program version and licensing information. Not that you can abbreviate this command.

--help, -h

Print a usage message summarizing the most useful command-line options. Not that you can abbreviate this command.

--dump-options

Print a list of all available options and commands. Not that you can abbreviate this command.

--server

Run in server mode and wait for commands on the stdin. This is default mode is to create a socket and listen for commands there.

--multi-server

Run in server mode and wait for commands on the stdin as well as on an additional Unix Domain socket. The server command GETINFO may be used to get the name of that extra socket.

--daemon

Run the program in the background. This option is required to prevent it from being accidentally running in the background.

6.2 Option Summary

--options file

Reads configuration from file instead of from the default per-user configuration file. The default configuration file is named scdaemon.conf and expected in the .gnupg directory directly below the home directory of the user.

--homedir dir

Set the name of the home directory to dir. If this option is not used, the home directory defaults to ~/.gnupg. It is only recognized when given on the command line. It also overrides any home directory stated through the environment variable GNUPGHOME or (on Windows systems) by means of the Registry entry HKCU\Software\GNU\GnuPG:HomeDir.

On Windows systems it is possible to install GnuPG as a portable application. In this case only this command line option is considered, all other ways to set a home directory are ignored.

To install GnuPG as a portable application under Windows, create an empty file name gpgconf.ctl in the same directory as the tool gpgconf.exe. The root of the installation is than that directory; or, if gpgconf.exe has been installed directly below a directory named bin, its parent directory. You also need to make sure that the following directories exist and are writable: ROOT/home for the GnuPG home and ROOT/usr/var/cache/gnupg for internal cache files.

-v

--verbose

Outputs additional information while running. You can increase the verbosity by giving several verbose commands to gpgsm, such as ‘-vv’.

--debug-level level

Select the debug level for investigating problems. level may be a numeric value or a keyword:

none

No debugging at all. A value of less than 1 may be used instead of the keyword.

basic

Some basic debug messages. A value between 1 and 2 may be used instead of the keyword.

advanced

More verbose debug messages. A value between 3 and 5 may be used instead of the keyword.

expert

Even more detailed messages. A value between 6 and 8 may be used instead of the keyword.

guru

All of the debug messages you can get. A value greater than 8 may be used instead of the keyword. The creation of hash tracing files is only enabled if the keyword is used.

How these messages are mapped to the actual debugging flags is not specified and may change with newer releases of this program. They are however carefully selected to best aid in debugging.

Note: All debugging options are subject to change and thus should not be used by any application program. As the name says, they are only used as helpers to debug problems.

--debug flags

This option is only useful for debugging and the behaviour may change at any time without notice. FLAGS are bit encoded and may be given in usual C-Syntax. The currently defined bits are:

0 (1)

command I/O

1 (2)

values of big number integers

2 (4)

low level crypto operations

5 (32)

memory allocation

6 (64)

caching

7 (128)

show memory statistics.

9 (512)

write hashed data to files named dbgmd-000*

10 (1024)

trace Assuan protocol. See also option --debug-assuan-log-cats.

11 (2048)

trace APDU I/O to the card. This may reveal sensitive data.

12 (4096)

trace some card reader related function calls.

--debug-all

Same as --debug=0xffffffff

--debug-wait n

When running in server mode, wait n seconds before entering the actual processing loop and print the pid. This gives time to attach a debugger.

--debug-ccid-driver

Enable debug output from the included CCID driver for smartcards. Using this option twice will also enable some tracing of the T=1 protocol. Note that this option may reveal sensitive data.

--debug-disable-ticker

This option disables all ticker functions like checking for card insertions.

--debug-allow-core-dump

For security reasons we won’t create a core dump when the process aborts. For debugging purposes it is sometimes better to allow core dump. This options enables it and also changes the working directory to /tmp when running in --server mode.

--debug-log-tid

This option appends a thread ID to the PID in the log output.

--debug-assuan-log-cats cats

Changes the active Libassuan logging categories to cats. The value for cats is an unsigned integer given in usual C-Syntax. A value of of 0 switches to a default category. If this option is not used the categories are taken from the environment variable ASSUAN_DEBUG. Note that this option has only an effect if the Assuan debug flag has also been with the option --debug. For a list of categories see the Libassuan manual.

--no-detach

Don’t detach the process from the console. This is mainly useful for debugging.

--log-file file

Append all logging output to file. This is very helpful in seeing what the agent actually does.

--pcsc-driver library

Use library to access the smartcard reader. The current default is libpcsclite.so. Instead of using this option you might also want to install a symbolic link to the default file name (e.g. from libpcsclite.so.1).

--ctapi-driver library

Use library to access the smartcard reader. The current default is libtowitoko.so. Note that the use of this interface is deprecated; it may be removed in future releases.

--disable-ccid

Disable the integrated support for CCID compliant readers. This allows falling back to one of the other drivers even if the internal CCID driver can handle the reader. Note, that CCID support is only available if libusb was available at build time.

--reader-port number_or_string

This option may be used to specify the port of the card terminal. A value of 0 refers to the first serial device; add 32768 to access USB devices. The default is 32768 (first USB device). PC/SC or CCID readers might need a string here; run the program in verbose mode to get a list of available readers. The default is then the first reader found.

To get a list of available CCID readers you may use this command:

echo scd getinfo reader_list \ | gpg-connect-agent --decode | awk '/^D/ {print $2}'

--card-timeout n

If n is not 0 and no client is actively using the card, the card will be powered down after n seconds. Powering down the card avoids a potential risk of damaging a card when used with certain cheap readers. This also allows applications that are not aware of Scdaemon to access the card. The disadvantage of using a card timeout is that accessing the card takes longer and that the user needs to enter the PIN again after the next power up.

Note that with the current version of Scdaemon the card is powered down immediately at the next timer tick for any value of n other than 0.

--enable-pinpad-varlen

Please specify this option when the card reader supports variable length input for pinpad (default is no). For known readers (listed in ccid-driver.c and apdu.c), this option is not needed. Note that if your card reader doesn’t supports variable length input but you want to use it, you need to specify your pinpad request on your card.

--disable-pinpad

Even if a card reader features a pinpad, do not try to use it.

--deny-admin

This option disables the use of admin class commands for card applications where this is supported. Currently we support it for the OpenPGP card. This commands is useful to inhibit accidental access to admin class command which could ultimately lock the card through wrong PIN numbers. Note that GnuPG versions older than 2.0.11 featured an --allow-admin command which was required to use such admin commands. This option has no more effect today because the default is now to allow admin commands.

--disable-application name

This option disables the use of the card application named name. This is mainly useful for debugging or if a application with lower priority should be used by default.