gnupg/doc/gpg.texi

\input texinfo
@setfilename gpg.info
@dircategory GnuPG
@direntry
* gpg: (gpg).                         GnuPG encryption and signing tool.
@end direntry

@node Top, , , (dir)
@top gpg
@chapheading Name

gpg --- encryption and signing tool
@chapheading Synopsis

@example
gpg
 --homedir name
 --options file
 options
 command
 args
  
@end example
@chapheading DESCRIPTION

@code{gpg} is the main program for the GnuPG system.

This man page only lists the commands and options available. For more
verbose documentation get the GNU Privacy Handbook (GPH) or one of the
other documents at http://www.gnupg.org/documentation/ .

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

@code{gpg} 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).

@code{gpg} recognizes these commands:

@table @asis

@item -s, --sign
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).

@item --clearsign
Make a clear text signature.

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

@item -e, --encrypt
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).

@item -c, --symmetric
Encrypt with a symmetric cipher using a passphrase. The default
symmetric cipher used is CAST5, 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).

@item --store
Store only (make a simple RFC1991 packet).

@item --decrypt 
Decrypt @code{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.

@item --verify 
Assume that @code{sigfile} is a signature and verify it
without generating any output. With no arguments,
the signature packet is read from stdin. 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. 
With more than
1 argument, the first should be a detached signature
and the remaining files are the signed stuff. To read the signed
stuff from stdin, use @samp{-} as the second filename.
For security reasons a detached signature cannot read the signed
material from stdin without denoting it in the above way.

@item --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.

@item --verify-files 
Identical to `--multifile --verify'.

@item --encrypt-files 
Identical to `--multifile --encrypt'.

@item --decrypt-files 
Identical to `--multifile --decrypt'.

@item --list-keys 
@itemx --list-public-keys 
List all keys from the public keyrings, or just the ones 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.

@item -K, --list-secret-keys 
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).

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

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").

@item --check-sigs 
Same as --list-sigs, but the signatures are verified.

@item --fingerprint 
List all keys 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.

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

@item --gen-key
Generate a new key pair. This command is normally only used
interactively.

There is an experimental feature which allows you to create keys
in batch mode. See the file @file{doc/DETAILS}
in the source distribution on how to use this.

@item --edit-key @code{name}
Present a menu which enables you to do all key
related tasks:

@table @asis

@item sign
Make a signature on key of user @code{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.

@item 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.

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

@item 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.
@end table

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.

@table @asis

@item 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.

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

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

@item adduid
Create an alternate user id.

@item 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).

@item deluid
Delete a user id.

@item delsig
Delete a signature.

@item revuid
Revoke a user id.

@item addkey
Add a subkey to this key.

@item addcardkey
Generate a key on a card and add it 
to this key.

@item keytocard
Transfer the selected secret key (or the primary key if no key 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.

@item delkey
Remove a subkey.

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

@item revkey
Revoke a subkey.

@item expire
Change the key 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.

@item passwd
Change the passphrase of the secret key.

@item 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.

@item uid @code{n}
Toggle selection of user id with index @code{n}.
Use 0 to deselect all.

@item key @code{n}
Toggle selection of subkey with index @code{n}.
Use 0 to deselect all.

@item check
Check all selected user ids.

@item showphoto
Display the selected photographic user
id.

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

@item 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.

@item setpref @code{string}
Set the list of user ID preferences to @code{string}, this should be a
string similar to the one printed by "pref". Using an empty string
will set the default preference string, using "none" will remove the
preferences. Use "gpg --version" to get a list of available
algorithms. This command just initializes an internal list and does
not change anything unless another command (such as "updpref") which
changes the self-signatures is used.

@item updpref
Change the preferences of all user IDs (or just of the selected ones
to the current list of preferences. The timestamp of all affected
self-signatures will be advanced by one second. 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.

@item 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-option honor-keyserver-url for more on how this works.
Note that some versions of PGP interpret the presence of a keyserver
URL as an instruction to enable PGP/MIME mail encoding. Setting a
value of "none" removes a existing preferred keyserver.

@item toggle
Toggle between public and secret key listing.

@item save
Save all changes to the key rings and quit.

@item quit
Quit the program without updating the
key rings.
@end table

The listing shows you the key with its secondary
keys and all user ids. 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:

@table @asis

@item -
No ownertrust assigned / not yet calculated.

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

@item q
Not enough information for calculation.

@item n
Never trust this key.

@item m
Marginally trusted.

@item f
Fully trusted.

@item u
Ultimately trusted.
@end table

@item --sign-key @code{name}
Signs a public key with your secret key. This is a shortcut version of
the subcommand "sign" from --edit.

@item --lsign-key @code{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.

@item --delete-key @code{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.

@item --delete-secret-key @code{name}
Remove key from the secret and public keyring. In batch mode the key
must be specified by fingerprint.

@item --delete-secret-and-public-key @code{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.

@item --gen-revoke @code{name}
Generate a revocation certificate for the complete key. To revoke
a subkey or a signature, use the --edit command.

@item --desig-revoke @code{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.

@item --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 new keyring is written to stdout or to
the file given with option "output". Use together
with --armor to mail those keys.

@item --send-keys 
Same as --export but sends the keys to a keyserver.
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.

@item --export-secret-keys 
@itemx --export-secret-subkeys 
Same as --export, but exports the secret keys instead.
This is normally not very useful and a security risk.
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.
See the option --simple-sk-checksum if you want to import such an
exported key with an older OpenPGP implementation.

@item --import 
@itemx --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 --keyserver-option merge-only option which
does not insert new keys but does only the merging of new signatures,
user-IDs and subkeys.

@item --recv-keys @code{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.

@item --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-option honor-keyserver-url).

@item --search-keys 
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.

@item --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.

@item --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.

@item --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 trust DB.

@item --import-ownertrust 
Update the trustdb with the ownertrust values stored
in @code{files} (or stdin if not given); existing
values will be overwritten.

@item --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.

@item --print-md @code{algo} 
@itemx --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.

@item --gen-random @code{0|1|2}  
Emit COUNT random bytes of the given quality level. If count is not given
or zero, an endless sequence of random bytes will be emitted.
PLEASE, don't use this command unless you know what you are doing; it may
remove precious entropy from the system!

@item --gen-prime @code{mode}  @code{bits}  
Use the source, Luke :-). The output format is still subject to change.

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

@item --warranty
Print warranty information.

@item -h, --help
Print usage information. This is a really long list even though it
doesn't list all options. For every option, consult this manual.
@end table
@chapheading OPTIONS

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.

@code{gpg} recognizes these options:

@table @asis

@item -a, --armor
Create ASCII armored output.

@item -o, --output @code{file}
Write output to @code{file}.

@item --max-output @code{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".

@item --mangle-dos-filenames
@itemx --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.

@item -u, --local-user @code{name}
Use @code{name} as the key to sign with. Note that this option
overrides --default-key.

@item --default-key @code{name}
Use @code{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.

@item -r, --recipient @code{name}
@itemx 
Encrypt for user id @code{name}. If this option or --hidden-recipient
is not specified, GnuPG asks for the user-id unless
--default-recipient is given.

@item -R, --hidden-recipient @code{name}
@itemx 
Encrypt for user id @code{name}, but hide the keyid of the key. This
option hides the receiver of the message and is a countermeasure
against traffic analysis. If this option or --recipient is not
specified, GnuPG asks for the user-id unless --default-recipient is
given.

@item --default-recipient @code{name}
Use @code{name} as default recipient if option --recipient is not used and
don't ask if this is a valid one. @code{name} must be non-empty.

@item --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.

@item --no-default-recipient
Reset --default-recipient and --default-recipient-self.

@item --encrypt-to @code{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.

@item --hidden-encrypt-to @code{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.

@item --no-encrypt-to
Disable the use of all --encrypt-to and --hidden-encrypt-to keys.

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

@item -q, --quiet
Try to be as quiet as possible.

@item -z @code{n}
@itemx --compress-level @code{n}
@itemx --bzip2-compress-level @code{n}
Set compression level to @code{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 @code{n} disables compression.

@item --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.

@item -t, --textmode
@itemx --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.

If -t (but not --textmode) is used together with armoring and signing,
this enables clearsigned messages. This kludge is needed for
command-line compatibility with command-line versions of PGP; normally
you would use --sign or --clearsign to select the type of the
signature.

@item -n, --dry-run
Don't make any changes (this is not completely implemented).

@item -i, --interactive
Prompt before overwriting any files.

@item --batch
@itemx --no-batch
Use batch mode. Never ask, do not allow interactive commands.
--no-batch disables this option.

@item --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 if --batch is used.

@item --yes
Assume "yes" on most questions.

@item --no
Assume "no" on most questions.

@item --ask-cert-level
@itemx --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.

@item --min-cert-level
When building the trust database, disregard any signatures with a
certification level below this. Defaults to 2, which disregards level
1 signatures.

@item --default-cert-level @code{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 that 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).

@item --trusted-key @code{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. 

@item --trust-model @code{pgp|classic|always}
Set what trust model GnuPG should follow. The models are:

@table @asis

@item 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.

@item classic
This is the standard Web of Trust as used in PGP 2.x and earlier.

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

@item always
Skip key validation and assume that used keys are always fully
trusted. You won't use this unless you have installed 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.
@end table

@item --always-trust
Identical to `--trust-model always'. This option is deprecated.

@item --keyid-format @code{short|0xshort|long|0xlong}
Select how to display key IDs. "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.

@item --keyserver @code{name}
Use @code{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 @code{name} is a URI: `scheme:[//]keyservername[:port]' The
scheme is the type of keyserver: "hkp" for the HTTP (or compatible)
keyservers, "ldap" for the NAI LDAP keyserver, 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.

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

@item --keyserver-options @code{parameters}
This is a space or comma delimited string that gives options for the
keyserver. Options can be prepended 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:

@table @asis

@item 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. Defaults to on.

@item 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.

@item honor-keyserver-url
When using --refresh-keys, if the key in question has a preferred
keyserver set, then use that preferred keyserver to refresh the key
from. Defaults to yes.

@item 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.

@item use-temp-files
On most Unix-like platforms, GnuPG communicates with the keyserver
helper program via pipes, which is the most efficient method. This
option forces GnuPG to use temporary files to communicate. On some
platforms (such as Win32 and RISC OS), this option is always enabled.

@item keep-temp-files
If using `use-temp-files', do not delete the temp files after using
them. This option is useful to learn the keyserver communication
protocol by reading the temporary files.

@item verbose
Tell the keyserver helper program to be more verbose. This option can
be repeated multiple times to increase the verbosity level.

@item 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.

@item http-proxy
For HTTP-like keyserver schemes that (such as HKP and HTTP itself),
try to access the keyserver over a proxy. If a @code{value} is
specified, use this as the HTTP proxy. If no @code{value} is
specified, try to use the value of the environment variable
"http_proxy".

@item 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.

Note that this option makes a "web bug" like behavior possible.
Keyserver 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.
@end table

@item --import-options @code{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:

@table @asis

@item 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.

@item 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.

@item merge-only
During import, allow key updates to existing keys, but do not allow
any new keys to be imported. Defaults to no.
@end table

@item --export-options @code{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:

@table @asis

@item 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.

@item 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.

@item export-sensitive-revkeys
Include designated revoker information that was marked as
"sensitive". Defaults to no.

@item export-minimal
Export the smallest key possible. Currently this is done by leaving
out any signatures that are not self-signatures. Defaults to no.
@end table

@item --list-options @code{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-' to give the opposite meaning.
The options are:

@table @asis

@item 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.

@item show-policy-urls
Show policy URLs in the --list-sigs or --check-sigs listings.
Defaults to no.

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

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

@item show-uid-validity
Display the calculated validity of user IDs during key listings.
Defaults to no.

@item show-unusable-uids
Show revoked and expired user IDs in key listings. Defaults to no.

@item show-unusable-subkeys
Show revoked and expired subkeys in key listings. Defaults to no.

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

@item show-sig-expire
Show signature expiration dates (if any) during --list-sigs or
--check-sigs listings. Defaults to no.

@item 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.
@end table

@item --verify-options @code{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:

@table @asis

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

@item show-policy-urls
Show policy URLs in the signature being verified. Defaults to no.

@item show-notations
@itemx show-std-notations
@itemx show-user-notations
Show all, IETF standard, or user-defined signature notations in the
signature being verified. Defaults to IETF standard.

@item show-keyserver-urls
Show any preferred keyserver URL in the signature being verified.
Defaults to no.

@item show-uid-validity
Display the calculated validity of the user IDs on the key that issued
the signature. Defaults to no.

@item show-unusable-uids
Show revoked and expired user IDs during signature verification.
Defaults to no.
@end table

@item --show-photos
@itemx --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.

@item --photo-viewer @code{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"),
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.

@item --exec-path @code{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.

@item --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.

@item --keyring @code{file}
Add @code{file} to the current list of keyrings. If @code{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.

@item --secret-keyring @code{file}
Same as --keyring but for the secret keyrings.

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

@item --trustdb-name @code{file}
Use @code{file} instead of the default trustdb. If @code{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).

@item --homedir @code{directory}
Set the name of the home directory to @code{directory} 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.

@item --display-charset @code{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. 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 @code{name} are:

@table @asis

@item iso-8859-1
This is the Latin 1 set.

@item iso-8859-2
The Latin 2 set.

@item iso-8859-15
This is currently an alias for
the Latin 1 set.

@item koi8-r
The usual Russian set (rfc1489).

@item utf-8
Bypass all translations and assume
that the OS uses native UTF-8 encoding.
@end table

@item --utf8-strings
@itemx --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.

@item --options @code{file}
Read options from @code{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.

@item --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.

@item --load-extension @code{name}
Load an extension module. If @code{name} does not contain a slash it is
searched for in the directory configured when GnuPG was built
(generally "/usr/local/lib/gnupg"). Extensions are not generally
useful anymore, and the use of this option is deprecated.

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

@item --debug-all
Set all useful debugging flags.

@item --debug-ccid-driver
Enable debug output from the included CCID driver for smartcards.
Note that this option is only available on some system.

@item --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.

@item --status-fd @code{n}
Write special status strings to the file descriptor @code{n}.
See the file DETAILS in the documentation for a listing of them.

@item --logger-fd @code{n}
Write log output to file descriptor @code{n} and not to stderr.

@item --attribute-fd @code{n}
Write attribute subpackets to the file descriptor @code{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.

@item --sk-comments
@itemx --no-sk-comments
Include secret key comment packets when exporting secret keys. This
is a GnuPG extension to the OpenPGP standard, and is off by default.
Please note that this has nothing to do with the comments in clear
text signatures or armor headers. --no-sk-comments disables this
option.

@item --comment @code{string}
@itemx --no-comments
Use @code{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.

@item --emit-version
@itemx --no-emit-version
Force inclusion of the version string in ASCII armored output.
--no-emit-version disables this option.

@item --sig-notation @code{name=value}
@itemx --cert-notation @code{name=value}
@itemx -N, --set-notation @code{name=value}
Put the name value pair into the signature as notation data.
@code{name} must consist only of printable characters or spaces, and
must contain a '@@' character. This is to help prevent pollution of
the IETF reserved notation namespace. The --expert flag overrides the
'@@' check. @code{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 @code{name} with an exclamation mark (!),
the notation data will be flagged as critical (rfc2440:5.2.3.15).
--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.

@item --show-notation
@itemx --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.

@item --sig-policy-url @code{string}
@itemx --cert-policy-url @code{string}
@itemx --set-policy-url @code{string}
Use @code{string} as a Policy URL for signatures (rfc2440:5.2.3.19).
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.

@item --show-policy-url
@itemx --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.

@item --sig-keyserver-url @code{string}
Use @code{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.

@item --set-filename @code{string}
Use @code{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.

@item --for-your-eyes-only
@itemx --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 the "secure viewer" with a Tempest-resistant font to
display the message. This option overrides --set-filename.
--no-for-your-eyes-only disables this option.

@item --use-embedded-filename
@itemx --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 allows to overwrite files. Defaults to no.

@item --completes-needed @code{n}
Number of completely trusted users to introduce a new
key signer (defaults to 1).

@item --marginals-needed @code{n}
Number of marginally trusted users to introduce a new
key signer (defaults to 3)

@item --max-cert-depth @code{n}
Maximum depth of a certification chain (default is 5).

@item --cipher-algo @code{name}
Use @code{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.

@item --digest-algo @code{name}
Use @code{name} as the message digest algorithm. Running the program
with the command --version yields a list of supported algorithms.

@item --compress-algo @code{name}
Use compression algorithm @code{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.

@item --cert-digest-algo @code{name}
Use @code{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.

@item --s2k-cipher-algo @code{name}
Use @code{name} as the cipher algorithm used to protect secret keys.
The default cipher is CAST5. This cipher is also used for
conventional encryption if --personal-cipher-preferences and
--cipher-algo is not given.

@item --s2k-digest-algo @code{name}
Use @code{name} as the digest algorithm used to mangle the passphrases.
The default algorithm is SHA-1.

@item --s2k-mode @code{n}
Selects how passphrases are mangled. If @code{n} is 0 a plain
passphrase (which is not recommended) will be used, a 1 adds a salt to
the passphrase and a 3 (the default) iterates the whole process a
couple of times. Unless --rfc1991 is used, this mode is also used for
conventional encryption.

@item --simple-sk-checksum
Secret keys are integrity protected by using a SHA-1 checksum. This
method is part of the upcoming enhanced OpenPGP specification but
GnuPG already uses it as a countermeasure against certain attacks.
Old applications don't understand this new format, so this option may
be used to switch back to the old behaviour. Using this option bears
a security risk. Note that using this option only takes effect when
the secret key is encrypted - the simplest way to make this happen is
to change the passphrase on the key (even changing it to the same
value is acceptable).

@item --disable-cipher-algo @code{name}
Never allow the use of @code{name} as cipher algorithm.
The given name will not be checked so that a later loaded algorithm
will still get disabled.

@item --disable-pubkey-algo @code{name}
Never allow the use of @code{name} as public key algorithm.
The given name will not be checked so that a later loaded algorithm
will still get disabled.

@item --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.

@item --no-sig-create-check
GnuPG normally verifies each signature right after creation to protect
against bugs and hardware malfunctions which could leak out bits from
the secret key. This extra verification needs some time (about 115%
for DSA keys), and so this option can be used to disable it.
However, due to the fact that the signature creation needs manual
interaction, this performance penalty does not matter in most settings.

@item --auto-check-trustdb
@itemx --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.

@item --throw-keyids
@itemx --no-throw-keyids
Do not put the recipient 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. --no-throw-keyids disables this
option.

@item --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.

@item --escape-from-lines
@itemx --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.

@item --passphrase-fd @code{n}
Read the passphrase from file descriptor @code{n}. If you use
0 for @code{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.

@item --command-fd @code{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.

@item --use-agent
@itemx --no-use-agent
Try to use the GnuPG-Agent. Please note that this agent is still under
development. With this option, GnuPG first tries to connect to the
agent before it asks for a passphrase. --no-use-agent disables this
option.

@item --gpg-agent-info
Override the value of the environment variable
@samp{GPG_AGENT_INFO}. This is only used when --use-agent has been given

@item 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.

@table @asis

@item --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.

@item --openpgp
Reset all packet, cipher and digest options to strict OpenPGP
behavior. Use this option to reset all previous options like
--rfc1991, --force-v3-sigs, --s2k-*, --cipher-algo, --digest-algo and
--compress-algo to OpenPGP compliant values. All PGP workarounds are
disabled.

@item --rfc2440
Reset all packet, cipher and digest options to strict RFC-2440
behavior. Note that this is currently the same thing as --openpgp.

@item --rfc1991
Try to be more RFC-1991 (PGP 2.x) compliant.

@item --pgp2
Set up all options to be as PGP 2.x compliant as possible, and warn if
an action is taken (e.g. encrypting to a non-RSA key) that will create
a message that PGP 2.x will not be able to handle. Note that `PGP
2.x' here means `MIT PGP 2.6.2'. There are other versions of PGP 2.x
available, but the MIT release is a good common baseline.

This option implies `--rfc1991 --disable-mdc --no-force-v4-certs
--no-sk-comment --escape-from-lines --force-v3-sigs
--no-ask-sig-expire --no-ask-cert-expire --cipher-algo IDEA
--digest-algo MD5 --compress-algo 1'. It also disables --textmode
when encrypting.

@item --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 --no-sk-comment --escape-from-lines
--force-v3-sigs --no-ask-sig-expire'

@item --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.

@item --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 SHA384 and SHA512 digests.
@end table

@item --force-v3-sigs
@itemx --no-force-v3-sigs
OpenPGP states that an implementation should generate v4 signatures
but PGP versions 5 through 7 only recognize v4 signatures on key
material. This option forces v3 signatures for signatures on data.
Note that this option overrides --ask-sig-expire, as v3 signatures
cannot have expiration dates. --no-force-v3-sigs disables this
option.

@item --force-v4-certs
@itemx --no-force-v4-certs
Always use v4 key signatures even on v3 keys. This option also
changes the default hash algorithm for v3 RSA keys from MD5 to SHA-1.
--no-force-v4-certs disables this option.

@item --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.

@item --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.

@item --allow-non-selfsigned-uid
@itemx --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.

@item --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.

@item --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.

@item --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 you there
is some clock problem. See also --ignore-time-conflict for timestamp
issues with signatures.

@item --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.

@item --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.

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

@item --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.

@item --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.

@item --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.

@item --no-verbose
Reset verbose level to 0.

@item --no-greeting
Suppress the initial copyright message.

@item --no-secmem-warning
Suppress the warning about "using insecure memory".

@item --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
supressed 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 supress
warnings about itself. The --homedir permissions warning may only be
supressed on the command line.

@item --no-mdc-warning
Suppress the warning about missing MDC integrity protection.

@item --require-secmem
@itemx --no-require-secmem
Refuse to run if GnuPG cannot get secure memory. Defaults to no
(i.e. run, but give a warning).

@item --no-armor
Assume the input data is not in ASCII armored format.

@item --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.

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

@item --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.

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

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

@item --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.

@item --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.

@item --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.

@item --no-literal
This is not for normal use. Use the source to see for what it might be useful.

@item --set-filesize
This is not for normal use. Use the source to see for what it might be useful.

@item --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. DON'T USE IT UNLESS YOU ARE REALLY
FORCED TO DO SO.

@item --override-session-key @code{string} 
Don't use the public key but the session key @code{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.

@item --ask-sig-expire
@itemx --no-ask-sig-expire
When making a data signature, prompt for an expiration time. If this
option is not specified, the expiration time is "never".
--no-ask-sig-expire disables this option.

@item --ask-cert-expire
@itemx --no-ask-cert-expire
When making a key signature, prompt for an expiration time. If this
option is not specified, the expiration time is "never".
--no-ask-cert-expire disables this option.

@item --expert
@itemx --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.

@item --allow-secret-key-import
This is an obsolete option and is not used anywhere.

@item --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) and might come handy in case where an encrypted
message contains a bogus key ID.

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

@item --no-expensive-trust-checks
Experimental use only.

@item --group @code{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 @code{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.

@item --ungroup @code{name}
Remove a given entry from the --group list.

@item --no-groups
Remove all entries from the --group list.

@item --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.

@item --personal-cipher-preferences @code{string}
Set the list of personal cipher preferences to @code{string}, this list
should be a string similar to the one printed by the command "pref" in
the edit menu. This allows the user to factor in their own preferred
algorithms when algorithms are chosen via recipient key preferences.
The most highly ranked cipher in this list is also used for the
--symmetric encryption command.

@item --personal-digest-preferences @code{string}
Set the list of personal digest preferences to @code{string}, this list
should be a string similar to the one printed by the command "pref" in
the edit menu. This allows the user to factor in their own preferred
algorithms when algorithms are chosen via recipient key preferences.
The most highly ranked digest algorithm in this list is algo used when
signing without encryption (e.g. --clearsign or --sign). The default
value is SHA-1.

@item --personal-compress-preferences @code{string}
Set the list of personal compression preferences to @code{string}, this
list should be a string similar to the one printed by the command
"pref" in the edit menu. This allows the user to factor in their own
preferred algorithms when algorithms are chosen via recipient key
preferences. The most highly ranked algorithm in this list is also
used when there are no recipient keys to consider (e.g. --symmetric).

@item --default-preference-list @code{string}
Set the list of default preferences to @code{string}, this list should
be a string similar to the one printed by the command "pref" in the
edit menu. This affects both key generation and "updpref" in the edit
menu.

@item --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
@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.
@end table
@chapheading How to specify a user ID

There are different ways to specify a user ID to GnuPG; here are some
examples:

@table @asis

@item 

@item 234567C4
@itemx 0F34E556E
@itemx 01347A56A
@itemx 0xAB123456
Here the key ID is given in the usual short form.

@item 234AABBCC34567C4
@itemx 0F323456784E56EAB
@itemx 01AB3FED1347A5612
@itemx 0x234AABBCC34567C4
Here the key ID is given in the long form as used by OpenPGP
(you can get the long key ID using the option --with-colons).

@item 1234343434343434C434343434343434
@itemx 123434343434343C3434343434343734349A3434
@itemx 0E12343434343434343434EAB3484343434343434
@itemx 0xE12343434343434343434EAB3484343434343434
The best way to specify a key ID is by using the fingerprint of
the key. This avoids any ambiguities in case that there are duplicated
key IDs (which are really rare for the long key IDs).

@item =Heinrich Heine <heinrichh@@uni-duesseldorf.de>
Using an exact to match string. The equal sign indicates this.

@item <heinrichh@@uni-duesseldorf.de>
Using the email address part which must match exactly. The left angle bracket
indicates this email address mode.

@item +Heinrich Heine duesseldorf
All words must match exactly (not case sensitive) but can appear in
any order in the user ID. Words are any sequences of letters,
digits, the underscore and all characters with bit 7 set.

@item Heine
@itemx *Heine
By case insensitive substring matching. This is the default mode but
applications may want to explicitly indicate this by putting the asterisk
in front.
@end table

Note that you can append an exclamation mark (!) to key IDs or
fingerprints. This flag tells GnuPG to use the specified primary or
secondary key and not to try and calculate which primary or secondary
key to use.
@chapheading 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.
@chapheading EXAMPLES

@table @asis

@item gpg -se -r @code{Bob} @code{file}
sign and encrypt for user Bob

@item gpg --clearsign @code{file}
make a clear text signature

@item gpg -sb @code{file}
make a detached signature

@item gpg --list-keys @code{user_ID}
show keys

@item gpg --fingerprint @code{user_ID}
show fingerprint

@item gpg --verify @code{pgpfile}
@itemx gpg --verify @code{sigfile} 
Verify the signature of the file but do not output the data. The
second form is used for detached signatures, where @code{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 @code{sigfile} or by asking the
user for the filename.
@end table
@chapheading ENVIRONMENT

@table @asis

@item HOME
Used to locate the default home directory.

@item GNUPGHOME
If set directory used instead of "~/.gnupg".

@item GPG_AGENT_INFO
Used to locate the gpg-agent; only honored when
--use-agent is set. The value consists of 3 colon delimited fields: 
The first is the path to the Unix Domain Socket, the second the PID of
the gpg-agent and the protocol version which should be set to 1. When
starting the gpg-agent as described in its documentation, this
variable is set to the correct value. The option --gpg-agent-info can
be used to override it.

@item http_proxy
Only honored when the keyserver-option
honor-http-proxy is set.

@item COLUMNS
@itemx LINES
Used to size some displays to the full size of the screen.
@end table
@chapheading FILES

@table @asis

@item ~/.gnupg/secring.gpg
The secret keyring

@item ~/.gnupg/secring.gpg.lock
and the lock file

@item ~/.gnupg/pubring.gpg
The public keyring

@item ~/.gnupg/pubring.gpg.lock
and the lock file

@item ~/.gnupg/trustdb.gpg
The trust database

@item ~/.gnupg/trustdb.gpg.lock
and the lock file

@item ~/.gnupg/random_seed
used to preserve the internal random pool

@item ~/.gnupg/gpg.conf
Default configuration file

@item ~/.gnupg/options
Old style configuration file; only used when gpg.conf
is not found

@item /usr[/local]/share/gnupg/options.skel
Skeleton options file

@item /usr[/local]/lib/gnupg/
Default location for extensions
@end table
@chapheading 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 @samp{-} to specify stdin.
@chapheading 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.
@chapheading BUGS

On many 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.

@bye