Unattended GPG key generation - Using the GNU Privacy Guard
Description: Using the GNU Privacy Guard

Up: Unattended Usage of GPG

### 3.6 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
  Enable (or disable) a mode where the command `passphrase` is ignored and instead the usual passphrase dialog is used. This does not make sense for batch key generation; however the unattended key generation feature is also used by GUIs and this feature relinquishes the GUI from implementing its own passphrase entry code. These are global control statements and affect all future key genrations.
%no-protection
  Since GnuPG version 2.1 it is not anymore possible to specify a passphrase for unattended key generation. The passphrase command is simply ignored and ‘`%ask-passpharse`’ is thus implicitly enabled. 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 not to use any 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 (2000-08-15) or as number of days, weeks, month or years. The special notation "seconds=N" is also allowed to directly give an Epoch value. 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.
Ceation-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. 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