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gpg

Section: GNU Tools (gpg.1)
Updated: 09 Sep 1998
Index

NAME

gpg - GNU Privacy Guard

SYNOPSIS

gpg [--homedir name] [--options file] [options] command [args]

gpgm [--homedir name] [--options file] [options] command [args]

DESCRIPTION

gpg is the main program for the GNUPG system. gpgm is a maintenancetool which has some commands gpgm does not have; it is there becauseit does not handle sensitive data ans therefore has no need to allocatesecure memory.

COMMANDS

gpg recognizes these commands:

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

--clearsign
Make a clear text signature.

-b, --detach-sign
Make a detached signature.

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

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

--store
store only (make a simple RFC1991 packet).

--decrypt [file]
    Decrypt file (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 [[sigfile] {signed-files}]
    Assume that 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
    .sig or .asc extension (if such a file does
    not exist it is expected at stdin - use - 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.

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

--list-keys    [names]

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

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

--list-sigs    [names]

    Same as --list-keys, but the signatures are listed
    too.

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

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

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

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

--edit-key name
    Present a menu which enables you to do all key
    related tasks:
    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.
    trust
      Change the owner trust value. This updates the
      trust-db immediately and no save is required.
    adduid
      Create an alternate user id.
    deluid
      Delete an user id.
    addkey
       Add a subkey to this key.
    delkey
       Remove a subkey.
    passwd
       Change the passphrase of the secret key.
    uid n
       Toggle selection of user id with index n.
       Use 0 to deselect all.
    key n
       Toggle selection of subkey with index n.
       Use 0 to deselect all.
    check
       Check all selected user ids.
    pref
       List preferences.
    toggle
       Toggle between public and secret key listing.
    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. 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:
      -  No ownertrust assigned.
      o  Trust not yet calculated.
      e  Trust calculation failed.
      q  Not enough information for calculation.
      n  Never trust this key.
      m  Marginally trusted.
      f  Fully trusted.
      u  Ultimately trusted

--delete-key
Remove key from the public keyring

--delete-secret-key
Remove key from the secret and public keyring

--gen-revoke
Generate a revocation certificate.

--export [names]
    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 new keyring is written to stdout or to
    the file given with option ``output''.  Use together
    with -a to mail those keys.

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

--import
import/merge keys

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

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

OPTIONS

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

gpg recognizes these options:

-a, --armor
Create ASCII armored output.

-o file, --output file
Write output to file.

-u name, --local-user name
    Use 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.

--default-key name
    Use 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.

-r name, --remote-user name
    Use 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.

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

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

-t, --textmode
Use canonical text mode. Used to make clear-text
signatures.

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

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

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

--yes
Assume yes on most questions.

--no
Assume no on most questions.

--keyring file
    Add file to the 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
    home-directory (~/.gnupg if --homedir) is not used.

--secret-keyring file
Same as --keyring but for secret keyrings.

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

--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 when used
    in an options file.

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

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

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

--debug-all
Set all useful debugging flags.

--status-fd n
Write special status strings to the file descriptor n.

--no-comment
Do not write comment packets.

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

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

--cipher-algo name
    Use name as cipher algorithm. Running the program
    with the option --verbose yields a list of supported
    algorithms. If this is not used the cipher algorithm is
    selected from the preferences stored with the key.

--digest-algo name
    Use name as message digest algorithm. Running the
    program with the option --verbose yields a list of
    supported algorithms.

--compress-algo number
    Use compress algorithm number. Default is 2 which is
    RFC1950 compression; you may use 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.

--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.

--passphrase-fd n
    Read the passphrase 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.
    Don't use this option if you can avoid it

--no-verbose
Reset verbose level to 0.

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

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

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

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

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

--with-colons
Print key listings delimited by colons.

--warranty
Print warranty information.

-h, --help
Print usage information.

RETURN VALUE

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

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

ENVIRONMENT

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

FILES

~/.gnupg/secring.gpg The secret keyring

~/.gnupg/pubring.gpg The public keyring

~/.gnupg/trustdb.gpg The trust database

~/.gnupg/options May contain options

/usr[/local]/lib/gnupg/ Default location for extensions

WARNINGS

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

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

BUGS

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

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gpg