gnupg/doc/gpg.1pod

=head1 NAME

gpg - GNU Privacy Guard

=head1 SYNOPSIS

B<gpg> [--homedir name] [--options file] [options] command [args]

B<gpgm> [--homedir name] [--options file] [options] command [args]

=head1 DESCRIPTION

B<gpg> is the main program for the GNUPG system. B<gpgm> is a maintenance
tool which has some commands B<gpgm> does not have; it is there because
it does not handle sensitive data and therefore has no need to allocate
secure memory.

=head1 COMMANDS

B<gpg> recognizes these commands:

B<-s>, B<--sign>
    Make a signature. This option may be combined
    with B<--encrypt>.

B<--clearsign>
    Make a clear text signature.

B<-b>, B<--detach-sign>
    Make a detached signature.

B<-e>, B<--encrypt>
    Encrypt data. This option may be combined with B<--sign>.

B<-c>, B<--symmetric>
    Encrypt with symmetric cipher only
    This command asks for a passphrase.

B<--store>
    store only (make a simple RFC1991 packet).

B<--decrypt> [I<file>]
    Decrypt file (or stdin if no file is specified) and
    write it to stdout (or the file specified with
    B<--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.

B<--verify> [[I<sigfile>] {I<signed-files>}]
    Assume that I<filename> is a signature and verify it
    without generating any output.  With no arguments,
    the signature packet is read from stdin (it may be a
    detached signature when not used in batch mode). If
    only a sigfile is given, it may be a complete
    signature or a detached signature, in which case
    the signed stuff is expected in a file without the
    I<.sig> or I<.asc> extension (if such a file does
    not exist it is expected at stdin - use B<-> as
    filename to force a read from stdin). With more than
    1 argument, the first should be a detached signature
    and the remaining files are the signed stuff.

B<-k> [I<username>] [I<keyring>]
    Kludge to be somewhat compatible with PGP.
    Without arguments, all public keyrings are listed.
    With one argument, only I<keyring> is listed.
    Special combinations are also allowed, but it may
    give strange results when combined with more options.
    B<-kv>    Same as B<-k>
    B<-kvv>   List the signatures with every key.
    B<-kvvv>  Additionally check all signatures.
    B<-kvc>   List fingerprints
    B<-kvvc>  List fingerprints and signatures

B<--list-keys>  [I<names>]
    List all keys from the public keyrings, or just the
    ones given on the command line.

B<--list-secret-keys> [I<names>]
    List all keys from the secret keyrings, or just the
    ones given on the command line.

B<--list-sigs>  [I<names>]
    Same as B<--list-keys>, but the signatures are listed
    too.

B<--check-sigs> [I<names>]
    Same as B<--list-sigs>, but the signatures are verified.

B<--fingerprint> [I<names>]
    List all keys with their fingerprints. This is the
    same output as B<list-keys> but with the additonal output
    of a line with the fingerprint. May also be combined
    with B<--list-sigs> or B<--check-sigs>.

B<--list-packets>
    List only the sequence of packets. This is mainly
    useful for debugging.

B<--gen-key>
    Generate a new key pair. This command can only be
    used interactive.


B<--edit-key> I<name>
    Present a menu which enables you to do all key
    related tasks:
    B<sign>
      Make a signature on key of user I<name>.
      If the key is not yet signed by the default
      user (or the users given with B<-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 B<-u>.
    B<trust>
      Change the owner trust value. This updates the
      trust-db immediately and no save is required.
    B<adduid>
      Create an alternate user id.
    B<deluid>
      Delete an user id.
    B<addkey>
       Add a subkey to this key.
    B<delkey>
       Remove a subkey.
    B<expire>
       Change the key expiration time.  If a key is
       select, the time of this key will be changed.
       With no selection the key expiration of the
       primary key is changed.
    B<passwd>
       Change the passphrase of the secret key.
    B<uid> I<n>
       Toggle selection of user id with index I<n>.
       Use 0 to deselect all.
    B<key> I<n>
       Toggle selection of subkey with index I<n>.
       Use 0 to deselect all.
    B<check>
       Check all selected user ids.
    B<pref>
       List preferences.
    B<toggle>
       Toggle between public and secret key listing.
    B<save>
       Save all changes to the key rings and quit.
    B<quit>
       Quit the program without updating the
       key rings.
    The listing shows you the key with its secondary
    keys and all user ids. Selected keys or user ids
    indicated by an asterisk. The trust value is
    displayed with the primary key: The first one is the
    assigned owner trust and the second the calculated
    trust value; letters are used for the values:
      B<->  No ownertrust assigned.
      B<o>  Trust not yet calculated.
      B<e>  Trust calculation failed.
      B<q>  Not enough information for calculation.
      B<n>  Never trust this key.
      B<m>  Marginally trusted.
      B<f>  Fully trusted.
      B<u>  Ultimately trusted


B<--delete-key>
    Remove key from the public keyring

B<--delete-secret-key>
    Remove key from the secret and public keyring

B<--gen-revoke>
    Generate a revocation certificate.

B<--export> [I<names>]
    Either export all keys from all keyrings (default
    keyrings and those registered via option B<--keyring>),
    or if at least one name is given, those of the given
    name. The new keyring is written to F<stdout> or to
    the file given with option "output".  Use together
    with B<-a> to mail those keys.


B<--export-secret-keys> [I<names>
    Same as B<--export>, but does export the secret keys.
    This is normally not very useful.

B<--import>, B<--fast-import>
    Import/merge keys.  The fast version does not build
    the trustdb; this can be deon at anytime with the
    command B<--update-trustdb>.

B<--export-ownertrust>
    List the assigned ownertrust values in ascii format
    for backup purposes [B<gpgm> only].

B<--import-ownertrust> [I<filename>]
    Update the trustdb with the ownertrust values stored
    in I<filename> (or stdin if not given); existing
    values will be overwritten. [B<gpgm> only].

=head1 OPTIONS

Long options can be put in an options file (default F<~/.gnupg/options>);
do not write the 2 dashes, but simply the name of the option and any
arguments if required.  Lines with a hash as the first non-white-space
character are ignored. Commands may be put in this file too, but that
does not make sense.

B<gpg> recognizes these options:


B<-a>, B<--armor>
    Create ASCII armored output.

B<-o> I<file>, B<--output> I<file>
    Write output to I<file>.

B<-u> I<name>, B<--local-user> I<name>
    Use I<name> as the user-id to sign.
    This option is silently ignored for the list commands,
    so that it can be used in an options file.

B<--default-key>  I<name>
    Use I<name> as default user-id for signatures.  If this
    is not used the default user-id is the first user-id
    from the secret keyring.

B<-r>  I<name>, B<--remote-user>  I<name>
    Use I<name> as the user-id for encryption.
    This option is silently ignored for the list commands,
    so that it can be used in an options file.

B<-v>, B<--verbose>
    Give more information during processing. If used
    twice, the input data is listed in detail.

B<-q>, B<--quiet>
    Be somewhat more quiet in some cases.

B<-z> I<n>
    Set compress level to I<n>. A value of 0 for I<n>
    disables compression. Default is to use the default
    compression level of zlib (which is 6).

B<-t>, B<--textmode>
    Use canonical text mode.  If B<-t> (but not
    B<--textmode>) is used together with armoring
    and signing, this enables clearsigned messages.
    This kludge is needed for PGP compatibility;
    normally you would use B<--sign> or b<--clearsign>
    to selected the type os signatures.

B<-n>, B<--dry-run>
    Don't make any changes (not yet implemented).

B<--batch>
    Batch mode; never ask, do not allow interactive
    commands.

B<--no-batch>
    Disable batch mode; this may be used if B<batch>
    is used in the options file.

B<--yes>
    Assume "yes" on most questions.

B<--no>
    Assume "no" on most questions.

B<--keyring> I<file>
    Add I<file> to the list of keyrings.
    If I<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
    home-directory (F<~/.gnupg> if B<--homedir>) is not used.
    The filename may be prefixed with a scheme:
      "gnupg-ring:" is the default one.
      "gnupg-gdbm:" may be used for a GDBM ring.

B<--secret-keyring> I<file>
    Same as B<--keyring> but for secret keyrings.


B<--homedir> I<dir>
    Set the name of the home directory to I<dir>. If this
    option is not used it defaults to F<~/.gnupg>. It does
    not make sense to use this in a options file. This
    also overrides the environment variable C<GNUPGHOME>.

B<--charset> I<name>
    Set the name of the native character set.  This is used
    to convert some strings to proper UTF-8 encoding.
    Valid values for I<name> are:
      B<iso-8859-1>  This is the default.
      B<koi8-r>      The usual Russian set (rfc1489).

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

B<--no-options>
    Shortcut for B<--options> I</dev/null>.  This option is
    detected before an attempt to open an option file.

B<--load-extension> I<modulename>
    Load an extension module. If I<modulename> does not
    contain a slash it is searched in B</usr/local/lib/gnupg>
    See the manual for more information about extensions.

B<--debug> I<flags>
    Set debugging flags. All flags are or-ed and I<flags> may
    be given in C syntax (e.g. 0x0042).

B<--debug-all>
    Set all useful debugging flags.

B<--status-fd> I<n>
    Write special status strings to the file descriptor I<n>.

B<--no-comment>
    Do not write comment packets.  This option affects only
    the generation of secret keys.  Output of option packets
    is disabled since version 0.4.2.

B<--comment> I<string>
    Use I<string> as comment string in clear text signatures.

B<--set-filename> I<string>
    Use I<string> as the name of file which is stored in
    messages.

B<--completes-needed> I<n>
    Number of completely trusted users to introduce a new
    key signator (defaults to 1).

B<--marginals-needed> I<n>
    Number of marginally trusted users to introduce a new
    key signator (defaults to 3)

B<--max-cert-depth> I<n>
    Maximum depth of a certification chain (default is 5).

B<--cipher-algo> I<name>
    Use I<name> as cipher algorithm. Running the program
    with the command B<--version> yields a list of supported
    algorithms. If this is not used the cipher algorithm is
    selected from the preferences stored with the key.

B<--digest-algo> I<name>
    Use I<name> as message digest algorithm. Running the
    program with the command B<--version> yields a list of
    supported algorithms.  Please note that using this
    option may violate the OpenPGP requirement, that a
    160 bit hash is to be used for DSA.

B<--s2k-cipher-algo> I<name>
    Use I<name> as the cipher algorithm used to protect secret
    keys.  The default cipher is BLOWFISH.  This cipher is
    also used for conventional encryption if B<--cipher-algo>
    is not given.

B<--s2k-digest-algo> I<name>
    Use I<name> as the digest algorithm used to mangle the
    passphrases.  The default algorithm is RIPE-MD-160.
    This digest algorithm is also used for conventional
    encryption if B<--digest-algo> is not given.

B<--s2k-mode> I<number>
    Selects how passphrases are mangled: A number of I<0>
    uses the plain passphrase (which is not recommended),
    a I<1> (default) adds a salt to the passphrase and
    I<3> interates the whole process a couple of times.
    Unless -B<--rfc1991> is used, this mode is also used
    for conventional encryption.

B<--compress-algo> I<number>
    Use compress algorithm I<number>. Default is I<2> which is
    RFC1950 compression; you may use I<1> to use the old zlib
    version which is used by PGP. This is only used for
    new messages. The default algorithm may give better
    results because the window size is not limited to 8K.
    If this is not used the OpenPGP behaviour is used; i.e.
    the compression algorith is selected from the preferences.

B<--digest-algo> I<name>
    Use I<name> as message digest algorithm. Running the
    program with the command B<--version> yields a list of
    supported algorithms.


B<--throw-keyid>
    Do not put the keyid into encrypted packets.  This option
    hides the receiver of the message and is a countermeasure
    against traffic analysis.  It may slow down the decryption
    process because all available secret keys are tried.

B<--passphrase-fd> I<n>
    Read the passphrase from file descriptor I<n>. If you use
    0 for I<n>, the passphrase will be read from stdin.  This
    can only be used if only one passphrase is supplied.
    B<Don't use this option if you can avoid it>

B<--rfc1991>
    Try to be more RFC1991 (PGP 2.x) compliant.

B<--force-v3-sigs>
    OpenPGP states that a implemenation should generate
    v4 signatures but PGP 5.x does only recognize such
    signatures on key material.  This options forces
    v3 signatures for signatures on data.

B<--no-verbose>
    Reset verbose level to 0.

B<--no-greeting>
    Suppress the initial copyright message but do not
    enter batch mode.

B<--no-armor>
    Assume the input data is not in ASCCI armored format.

B<--no-default-keyring>
    Do not add the default keyrings to the list of
    keyrings.

B<--skip-verify>
    Skip the signature verification step.  This may be
    used to make the encryption faster if the signature
    verification is not needed.

B<--version>
    Print version information along with a list
    of supported algorithms.

B<--with-colons>
    Print key listings delimited by colons.

B<--warranty>
    Print warranty information.

B<-h>, B<--help>
    Print usage information.


=head1 RETURN VALUE

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

=head1 EXAMPLES

  -se -r Bob [file]          sign and encrypt for user Bob
  -sat [file]                make a clear text signature
  -sb  [file]                make a detached signature
  -k   [userid]              show keys
  -kc  [userid]              show fingerprint

=head1 ENVIRONMENT

C<HOME>       Used to locate the default home directory.
C<GNUPGHOME>  If set, direcory used instead of F<~/.gnupg>.

=head1 FILES

F<~/.gnupg/secring.gpg>     The secret keyring

F<~/.gnupg/pubring.gpg>     The public keyring

F<~/.gnupg/trustdb.gpg>     The trust database

F<~/.gnupg/options>         May contain options

F</usr[/local]/lib/gnupg/>  Default location for extensions

=head1 SEE ALSO

gpg(1)  gpgm(1)


=head1 WARNINGS

Use a B<good> password for your user account and a B<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 B<~/.gnupg/>
directory very good.

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

=head1 BUGS

On many systems this program should be installed as setuid(root); this
is necessary to lock some pages of memory. If you get no warning message
about insecure memory your OS kernel supports locking without being root;
setuid is dropped as soon as this memory is allocated.