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gpg(1) gpg(1)
NAME
gpg — encryption and signing tool
SYNOPSIS
gpg [--homedir name] [--options file] [options] command [args]
DESCRIPTION
gpg is the main program for the GnuPG system.
This man page only lists the commands and options available. For more verbose doc-
umentation 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 "--".
COMMANDS
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).
gpg recognizes these commands:
-s, --sign [file]
Make a signature. This command may be combined with --encrypt (for a
signed and encrypted message), --symmetric (for a signed and symmetri-
cally encrypted message), or --encrypt and --symmetric together (for a
signed message that may be decrypted via a secret key or a passphrase).
--clearsign [file]
Make a clear text signature. The content in a clear text signature is
readable without any special software. OpenPGP software is only needed
to verify the signature. Clear text signatures may modify end-of-line
whitespace for platform independence and are not intended to be
reversible.
-b, --detach-sign [file]
Make a detached signature.
-e, --encrypt [file]
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).
-c, --symmetric [file]
Encrypt with a symmetric cipher using a passphrase. The default symmet-
ric cipher used is CAST5, but may be chosen with the --cipher-algo
option. This option may be combined with --sign (for a signed and sym-
metrically encrypted message), --encrypt (for a message that may be
decrypted via a secret key or a passphrase), or --sign and --encrypt
together (for a signed message that may be decrypted via a secret key or
a passphrase).
--store [file]
Store only (make a simple RFC1991 packet).
-d, --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 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 - as the second file-
name. For security reasons a detached signature cannot read the signed
material from stdin without denoting it in the above way.
--multifile
This modifies certain other commands to accept multiple files for pro-
cessing on the command line or read from stdin with each filename on a
separate line. This allows for many files to be processed at once.
--multifile may currently be used along with --verify, --encrypt, and
--decrypt. Note that ‘--multifile --verify’ may not be used with
detached signatures.
--verify-files [files]
Identical to ‘--multifile --verify’.
--encrypt-files [files]
Identical to ‘--multifile --encrypt’.
--decrypt-files [files]
Identical to ‘--multifile --decrypt’.
--list-keys [names]
--list-public-keys [names]
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.
-K, --list-secret-keys [names]
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).
--list-sigs [names]
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 signa-
ture. From left to right, they are the numbers 1-3 for certificate check
level (see --ask-cert-level), "L" for a local or non-exportable signature
(see --lsign-key), "R" for a nonRevocable signature (see the --edit-key
command "nrsign"), "P" for a signature that contains a policy URL (see
--cert-policy-url), "N" for a signature that contains a notation (see
--cert-notation), "X" for an eXpired signature (see --ask-cert-expire),
and the numbers 1-9 or "T" for 10 and above to indicate trust signature
levels (see the --edit-key command "tsign").
--check-sigs [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 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.
--list-packets
List only the sequence of packets. This is mainly useful for debugging.
--gen-key Generate a new key pair. This command is normally only used interac-
tively.
There is an experimental feature which allows you to create keys in batch
mode. See the file doc/DETAILS in the source distribution on how to use
this.
--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.
lsign Same as "sign" but the signature is marked as non-exportable
and will therefore never be used by others. This may be used
to make keys valid only in the local environment.
nrsign Same as "sign" but the signature is marked as non-revocable and
can therefore never be revoked.
tsign Make a trust signature. This is a signature that combines the
notions of certification (like a regular signature), and trust
(like the "trust" command). It is generally only useful in
distinct communities or groups.
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.
revsig Revoke a signature. For every signature which has been gener-
ated by one of the secret keys, GnuPG asks whether a revocation
certificate should be generated.
trust Change the owner trust value. This updates the trust-db immedi-
ately and no save is required.
disable
enable Disable or enable an entire key. A disabled key can not nor-
mally be used for encryption.
adduid Create an alternate user id.
addphoto Create a photographic user id. This will prompt for a JPEG
file that will be embedded into the user ID. Note that a very
large JPEG will make for a very large key. Also note that some
programs will display your JPEG unchanged (GnuPG), and some
programs will scale it to fit in a dialog box (PGP).
deluid Delete a user id.
delsig Delete a signature.
revuid Revoke a user id.
addkey Add a subkey to this key.
addcardkey
Generate a key on a card and add it to this key.
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.
bkuptocard file
Restore the given file to a card. This command may be used to
restore a backup key (as generated during card initialization)
to a new card. In almost all cases this will be the encryption
key. You should use this command only with the corresponding
public key and make sure that the file given as argument is
indeed the backup to restore. You should then select 2 to
restore as encryption key. You will first be asked to enter
the passphrase of the backup key and then for the Admin PIN of
the card.
delkey Remove a subkey.
addrevoker [sensitive]
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).
revkey Revoke a subkey.
expire Change the key expiration time. If a subkey is selected, the
expiration time of this subkey will be changed. With no selec-
tion, the key expiration of the primary key is changed.
passwd Change the passphrase of the secret key.
primary Flag the current user id as the primary one, removes the pri-
mary user id flag from all other user ids and sets the times-
tamp 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.
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.
showphoto Display the selected photographic user id.
pref List preferences from the selected user ID. This shows the
actual preferences, without including any implied preferences.
showpref More verbose preferences listing for the selected user ID.
This shows the preferences in effect by including the implied
preferences of 3DES (cipher), SHA-1 (digest), and Uncompressed
(compression) if they are not already included in the prefer-
ence list. In addition, the preferred keyserver and signature
notations (if any) are shown.
setpref string
Set the list of user ID preferences to string for all (or just
the selected) user IDs. Calling setpref with no arguments sets
the preference list to the default (either built-in or set via
--default-preference-list), and calling setpref with "none" as
the argument sets an empty preference list. Use "gpg
--version" to get a list of available algorithms. Note that
while you can change the preferences on an attribute user ID
(aka "photo ID"), GnuPG does not select keys via attribute user
IDs so these preferences will not be used by GnuPG.
keyserver Set a preferred keyserver for the specified user ID(s). This
allows other users to know where you prefer they get your key
from. See --keyserver-options honor-keyserver-url for more on
how this works. Setting a value of "none" removes an existing
preferred keyserver.
notation Set a name=value notation for the specified user ID(s). See
--cert-notation for more on how this works. Setting a value of
"none" removes all notations, setting a notation prefixed with
a minus sign (-) removes that notation, and setting a notation
name (without the =value) prefixed with a minus sign removes
all notations with that name.
toggle Toggle between public and secret key listing.
clean Compact (by removing all signatures except the selfsig) any
user ID that is no longer usable (e.g. revoked, or expired).
Then, remove any signatures that are not usable by the trust
calculations. Specifically, this removes any signature that
does not validate, any signature that is superseded by a later
signature, revoked signatures, and signatures issued by keys
that are not present on the keyring.
minimize Make the key as small as possible. This removes all signatures
from each user ID except for the most recent self-signature.
cross-certify
Add cross-certification signatures to signing subkeys that may
not currently have them. Cross-certification signatures pro-
tect against a subtle attack against signing subkeys. See
--require-cross-certification.
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 are indicated by an asterisk. The trust value
is displayed with the primary key: the first is the assigned owner trust
and the second is the calculated trust value. Letters are used for the
values:
- No ownertrust assigned / not yet calculated.
e Trust calculation has failed; probably due to an expired key.
q Not enough information for calculation.
n Never trust this key.
m Marginally trusted.
f Fully trusted.
u Ultimately trusted.
--card-edit
Present a menu to work with a smartcard. The subcommand "help" provides
an overview on available commands. For a detailed description, please
see the Card HOWTO at http://www.gnupg.org/documentation/how-
tos.html#GnuPG-cardHOWTO .
--card-status
Show the content of the smart card.
--change-pin
Present a menu to allow changing the PIN of a smartcard. This function-
ality is also available as the subcommand "passwd" with the --card-edit
command.
--sign-key name
Signs a public key with your secret key. This is a shortcut version of
the subcommand "sign" from --edit.
--lsign-key name
Signs a public key with your secret key but marks it as non-exportable.
This is a shortcut version of the subcommand "lsign" from --edit.
--delete-key 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 safe-
guard against accidental deletion of multiple keys.
--delete-secret-key name
Remove key from the secret and public keyring. In batch mode the key must
be specified by fingerprint.
--delete-secret-and-public-key name
Same as --delete-key, but if a secret key exists, it will be removed
first. In batch mode the key must be specified by fingerprint.
--gen-revoke name
Generate a revocation certificate for the complete key. To revoke a sub-
key or a signature, use the --edit command.
--desig-revoke name
Generate a designated revocation certificate for a key. This allows a
user (with the permission of the keyholder) to revoke someone else’s key.
--export [names]
Either export all keys from all keyrings (default keyrings and those reg-
istered 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.
--send-keys [names]
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.
--export-secret-keys [names]
--export-secret-subkeys [names]
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 use-
less; 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.
--import [files]
--fast-import [files]
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-options merge-only option which does not
insert new keys but does only the merging of new signatures, user-IDs and
subkeys.
--recv-keys key IDs
Import the keys with the given key IDs from a keyserver. Option --key-
server must be used to give the name of this keyserver.
--refresh-keys [key IDs]
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 key-
server for all keys that do not have preferred keyservers set (see --key-
server-options honor-keyserver-url).
--search-keys names
Search the keyserver for the given names. Multiple names given here will
be joined together to create the search string for the keyserver. Option
--keyserver must be used to give the name of this keyserver. Keyservers
that support different search methods allow using the syntax specified in
"How to specify a user ID" below. Note that different keyserver types
support different search methods. Currently only LDAP supports them all.
--fetch-keys URIs
Retrieve keys located at the specified URIs. Note that different instal-
lations of GnuPG may support different protocols (HTTP, FTP, LDAP, etc.)
--update-trustdb
Do trust database maintenance. This command iterates over all keys and
builds the Web of Trust. This is an interactive command because it may
have to ask for the "ownertrust" values for keys. The user has to give
an estimation of how far she trusts the owner of the displayed key to
correctly certify (sign) other keys. GnuPG only asks for the ownertrust
value if it has not yet been assigned to a key. Using the --edit-key
menu, the assigned value can be changed at any time.
--check-trustdb
Do trust database maintenance without user interaction. From time to
time the trust database must be updated so that expired keys or signa-
tures and the resulting changes in the Web of Trust can be tracked. Nor-
mally, 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 "own-
ertrust".
For use with cron jobs, this command can be used together with --batch in
which case the trust database check is done only if a check is needed.
To force a run even in batch mode add the option --yes.
--export-ownertrust
Send the ownertrust values to stdout. This is useful for backup purposes
as these values are the only ones which can’t be re-created from a cor-
rupted trust DB.
--import-ownertrust [files]
Update the trustdb with the ownertrust values stored in files (or stdin
if not given); existing values will be overwritten.
--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 situ-
ations too.
--print-md algo [files]
--print-mds [files]
Print message digest of algorithm ALGO for all given files or stdin.
With the second form (or a deprecated "*" as algo) digests for all avail-
able algorithms are printed.
--gen-random 0|1|2 [count]
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!
--gen-prime mode bits [qbits]
Use the source, Luke :-). The output format is still subject to change.
--version Print version information along with a list of supported algorithms.
--warranty
Print warranty information.
-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.
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.
gpg recognizes these options:
-a, --armor
Create ASCII armored output.
-o, --output file
Write output to file.
--max-output n
This option sets a limit on the number of bytes that will be generated
when processing a file. Since OpenPGP supports various levels of com-
pression, 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 maxi-
mum file size that will be generated before processing is forced to stop
by the OS limits. Defaults to 0, which means "no limit".
--mangle-dos-filenames
--no-mangle-dos-filenames
Older version of Windows cannot handle filenames with more than one dot.
--mangle-dos-filenames causes GnuPG to replace (rather than add to) the
extension of an output filename to avoid this problem. This option is
off by default and has no effect on non-Windows platforms.
-u, --local-user name
Use name as the key to sign with. Note that this option overrides
--default-key.
--default-key name
Use name as the default key to sign with. If this option is not used,
the default key is the first key found in the secret keyring. Note that
-u or --local-user overrides this option.
-r, --recipient name
Encrypt for user id name. If this option or --hidden-recipient is not
specified, GnuPG asks for the user-id unless --default-recipient is
given.
-R, --hidden-recipient name
Encrypt for user ID name, but hide the key ID of this user’s key. This
option helps to hide the receiver of the message and is a limited coun-
termeasure against traffic analysis. If this option or --recipient is
not specified, GnuPG asks for the user ID unless --default-recipient is
given.
--default-recipient name
Use name as default recipient if option --recipient is not used and don’t
ask if this is a valid one. name must be non-empty.
--default-recipient-self
Use the default key as default recipient if option --recipient is not
used and don’t ask if this is a valid one. The default key is the first
one from the secret keyring or the one set with --default-key.
--no-default-recipient
Reset --default-recipient and --default-recipient-self.
--encrypt-to name
Same as --recipient but this one is intended for use in the options file
and may be used with your own user-id as an "encrypt-to-self". These
keys are only used when there are other recipients given either by use of
--recipient or by the asked user id. No trust checking is performed for
these user ids and even disabled keys can be used.
--hidden-encrypt-to name
Same as --hidden-recipient but this one is intended for use in the
options file and may be used with your own user-id as a hidden "encrypt-
to-self". These keys are only used when there are other recipients given
either by use of --recipient or by the asked user id. No trust checking
is performed for these user ids and even disabled keys can be used.
--no-encrypt-to
Disable the use of all --encrypt-to and --hidden-encrypt-to keys.
-v, --verbose
Give more information during processing. If used twice, the input data is
listed in detail.
-q, --quiet
Try to be as quiet as possible.
-z n
--compress-level n
--bzip2-compress-level n
Set compression level to n for the ZIP and ZLIB compression algorithms.
The default is to use the default compression level of zlib (normally 6).
--bzip2-compress-level sets the compression level for the BZIP2 compres-
sion algorithm (defaulting to 6 as well). This is a different option
from --compress-level since BZIP2 uses a significant amount of memory for
each additional compression level. -z sets both. A value of 0 for n
disables compression.
--bzip2-decompress-lowmem
Use a different decompression method for BZIP2 compressed files. This
alternate method uses a bit more than half the memory, but also runs at
half the speed. This is useful under extreme low memory circumstances
when the file was originally compressed at a high --bzip2-compress-level.
-t, --textmode
--no-textmode
Treat input files as text and store them in the OpenPGP canonical text
form with standard "CRLF" line endings. This also sets the necessary
flags to inform the recipient that the encrypted or signed data is text
and may need its line endings converted back to whatever the local system
uses. This option is useful when communicating between two platforms
that have different line ending conventions (UNIX-like to Mac, Mac to
Windows, etc). --no-textmode disables this option, and is the default.
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.
-n, --dry-run
Don’t make any changes (this is not completely implemented).
-i, --interactive
Prompt before overwriting any files.
--batch
--no-batch
Use batch mode. Never ask, do not allow interactive commands. --no-
batch disables this option.
--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.
--yes Assume "yes" on most questions.
--no Assume "no" on most questions.
--ask-cert-level
--no-ask-cert-level
When making a key signature, prompt for a certification level. If this
option is not specified, the certification level used is set via
--default-cert-level. See --default-cert-level for information on the
specific levels and how they are used. --no-ask-cert-level disables this
option. This option defaults to no.
--default-cert-level n
The default to use for the check level when signing a key.
0 means you make no particular claim as to how carefully you verified the
key.
1 means you believe the key is owned by the person who claims to own it
but you could not, or did not verify the key at all. This is useful for
a "persona" verification, where you sign the key of a pseudonymous user.
2 means you did casual verification of the key. For example, this could
mean that you verified 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).
--min-cert-level
When building the trust database, treat any signatures with a certifica-
tion level below this as invalid. Defaults to 2, which disregards level
1 signatures. Note that level 0 "no particular claim" signatures are
always accepted.
--trusted-key long key ID
Assume that the specified key (which must be given as a full 8 byte key
ID) is as trustworthy as one of your own secret keys. This option is use-
ful if you don’t want to keep your secret keys (or one of them) online
but still want to be able to check the validity of a given recipient’s or
signator’s key.
--trust-model pgp|classic|direct|always|auto
Set what trust model GnuPG should follow. The models are:
pgp This is the Web of Trust combined with trust signatures as used
in PGP 5.x and later. This is the default trust model when
creating a new trust database.
classic This is the standard Web of Trust as used in PGP 2.x and ear-
lier.
direct Key validity is set directly by the user and not calculated via
the Web of Trust.
always Skip key validation and assume that used keys are always fully
trusted. You generally won’t use this unless you are using
some external validation scheme. This option also suppresses
the "[uncertain]" tag printed with signature checks when there
is no evidence that the user ID is bound to the key.
auto Select the trust model depending on whatever the internal trust
database says. This is the default model if such a database
already exists.
--always-trust
Identical to ‘--trust-model always’. This option is deprecated.
--auto-key-locate parameters
--no-auto-key-locate
GnuPG can automatically locate and retrieve keys as needed using this
option. This happens when encrypting to an email address (in the
"user AT example.com" form), and there are no user AT example.com keys on the
local keyring. This option takes any number of the following arguments,
in the order they are to be tried:
cert locate a key using DNS CERT, as specified in 2538bis (currently
in draft): http://www.josefsson.org/rfc2538bis/
pka locate a key using DNS PKA.
ldap locate a key using the PGP Universal method of checking
"ldap://keys.(thedomain)".
keyserver locate a key using whatever keyserver is defined using the
--keyserver option.
(keyserver URL)
In addition, a keyserver URL as used in the --keyserver option
may be used here to query that particular keyserver.
--keyid-format 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.
--keyserver name [name=value1 value2 value3 ...]
Use name as your keyserver. This is the server that --recv-keys, --send-
keys, and --search-keys will communicate with to receive keys from, send
keys to, and search for keys on. The format of the name is a URI:
‘scheme:[//]keyservername[:port]’ The scheme is the type of keyserver:
"hkp" for the HTTP (or compatible) keyservers, "ldap" for the LDAP key-
servers, or "mailto" for the Graff email keyserver. Note that your par-
ticular installation of GnuPG may have other keyserver types available as
well. Keyserver schemes are case-insensitive. After the keyserver name,
optional keyserver configuration options may be provided. These are the
same as the global --keyserver-options from below, but apply only to this
particular keyserver.
Most keyservers synchronize with each other, so there is generally no
need to send keys to more than one server. The keyserver "hkp://sub-
keys.pgp.net" uses round robin DNS to give a different keyserver each
time you use it.
--keyserver-options name=value1 [value2 value3 ...]
This is a space or comma delimited string that gives options for the key-
server. Options can be prepended with a ‘no-’ to give the opposite mean-
ing. Valid import-options or export-options may be used here as well to
apply to importing (--recv-key) or exporting (--send-key) a key from a
keyserver. While not all options are available for all keyserver types,
some common options are:
include-revoked
When searching for a key with --search-keys, include keys that
are marked on the keyserver as revoked. Note that not all key-
servers 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 skip-
ping keys that are incorrectly marked as revoked.
include-disabled
When searching for a key with --search-keys, include keys that
are marked on the keyserver as disabled. Note that this option
is not used with HKP keyservers.
auto-key-retrieve
This 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 send-
ing 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.
honor-keyserver-url
When using --refresh-keys, if the key in question has a pre-
ferred keyserver URL, then use that preferred keyserver to
refresh the key from. In addition, if auto-key-retrieve is
set, and the signature being verified has a preferred keyserver
URL, then use that preferred keyserver to fetch the key from.
Defaults to yes.
honor-pka-record
If auto-key-retrieve is set, and the signature being verified
has a PKA record, then use the PKA information to fetch the
key. Defaults to yes.
include-subkeys
When receiving a key, include subkeys as potential targets.
Note that this option is not used with HKP keyservers, as they
do not support retrieving keys by subkey id.
use-temp-files
On most Unix-like platforms, GnuPG communicates with the key-
server 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.
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 com-
munication protocol by reading the temporary files.
verbose Tell the keyserver helper program to be more verbose. This
option can be repeated multiple times to increase the verbosity
level.
timeout[=value]
Tell the keyserver helper program how long (in seconds) to try
and perform a keyserver action before giving up. Note that
performing multiple actions at the same time uses this timeout
value per action. For example, when retrieving multiple keys
via --recv-keys, the timeout applies separately to each key
retrieval, and not to the --recv-keys command as a whole.
Defaults to 30 seconds.
http-proxy[=value]
For HTTP-like keyserver schemes that (such as HKP and HTTP
itself), try to access the keyserver over a proxy. If a value
is specified, use this as the HTTP proxy. If no value is spec-
ified, the value of the environment variable "http_proxy", if
any, will be used.
max-cert-size[=value]
When retrieving a key via DNS CERT, only accept keys up to this
size. Defaults to 16384 bytes.
--import-options parameters
This is a space or comma delimited string that gives options for import-
ing keys. Options can be prepended with a ‘no-’ to give the opposite
meaning. The options are:
import-local-sigs
Allow importing key signatures marked as "local". This is not
generally useful unless a shared keyring scheme is being used.
Defaults to no.
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 multi-
ple subkeys. Note that this cannot completely repair the dam-
aged 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.
merge-only
During import, allow key updates to existing keys, but do not
allow any new keys to be imported. Defaults to no.
import-clean
After import, compact (remove all signatures except the self-
signature) any user IDs from the new key that are not usable.
Then, remove any signatures from the new key that are not
usable. This includes signatures that were issued by keys that
are not present on the keyring. This option is the same as
running the --edit-key command "clean" after import. Defaults
to no.
import-minimal
Import the smallest key possible. This removes all signatures
except the most recent self-signature on each user ID. This
option is the same as running the --edit-key command "minimize"
after import. Defaults to no.
--export-options parameters
This is a space or comma delimited string that gives options for export-
ing keys. Options can be prepended with a ‘no-’ to give the opposite
meaning. The options are:
export-local-sigs
Allow exporting key signatures marked as "local". This is not
generally useful unless a shared keyring scheme is being used.
Defaults to no.
export-attributes
Include attribute user IDs (photo IDs) while exporting. This
is useful to export keys if they are going to be used by an
OpenPGP program that does not accept attribute user IDs.
Defaults to yes.
export-sensitive-revkeys
Include designated revoker information that was marked as "sen-
sitive". Defaults to no.
export-reset-subkey-passwd
When using the "--export-secret-subkeys" command, this option
resets the passphrases for all exported subkeys to empty. This
is useful when the exported subkey is to be used on an unat-
tended machine where a passphrase doesn’t necessarily make
sense. Defaults to no.
export-clean
Compact (remove all signatures from) user IDs on the key being
exported if the user IDs are not usable. Also, do not export
any signatures that are not usable. This includes signatures
that were issued by keys that are not present on the keyring.
This option is the same as running the --edit-key command
"clean" before export except that the local copy of the key is
not modified. Defaults to no.
export-minimal
Export the smallest key possible. This removes all signatures
except the most recent self-signature on each user ID. This
option is the same as running the --edit-key command "minimize"
before export except that the local copy of the key is not mod-
ified. Defaults to no.
--list-options parameters
This is a space or comma delimited string that gives options used when
listing keys and signatures (that is, --list-keys, --list-sigs, --list-
public-keys, --list-secret-keys, and the --edit-key functions). Options
can be prepended with a ‘no-’ to give the opposite meaning. The options
are:
show-photos
Causes --list-keys, --list-sigs, --list-public-keys, and
--list-secret-keys to display any photo IDs attached to the
key. Defaults to no. See also --photo-viewer.
show-policy-urls
Show policy URLs in the --list-sigs or --check-sigs listings.
Defaults to no.
show-notations
show-std-notations
show-user-notations
Show all, IETF standard, or user-defined signature notations in
the --list-sigs or --check-sigs listings. Defaults to no.
show-keyserver-urls
Show any preferred keyserver URL in the --list-sigs or --check-
sigs listings. Defaults to no.
show-uid-validity
Display the calculated validity of user IDs during key list-
ings. Defaults to no.
show-unusable-uids
Show revoked and expired user IDs in key listings. Defaults to
no.
show-unusable-subkeys
Show revoked and expired subkeys in key listings. Defaults to
no.
show-keyring
Display the keyring name at the head of key listings to show
which keyring a given key resides on. Defaults to no.
show-sig-expire
Show signature expiration dates (if any) during --list-sigs or
--check-sigs listings. Defaults to no.
show-sig-subpackets
Include signature subpackets in the key listing. This option
can take an optional argument list of the subpackets to list.
If no argument is passed, list all subpackets. Defaults to no.
This option is only meaningful when using --with-colons along
with --list-sigs or --check-sigs.
--verify-options parameters
This is a space or comma delimited string that gives options used when
verifying signatures. Options can be prepended with a ‘no-’ to give the
opposite meaning. The options are:
show-photos
Display any photo IDs present on the key that issued the signa-
ture. Defaults to no. See also --photo-viewer.
show-policy-urls
Show policy URLs in the signature being verified. Defaults to
no.
show-notations
show-std-notations
show-user-notations
Show all, IETF standard, or user-defined signature notations in
the signature being verified. Defaults to IETF standard.
show-keyserver-urls
Show any preferred keyserver URL in the signature being veri-
fied. Defaults to no.
show-uid-validity
Display the calculated validity of the user IDs on the key that
issued the signature. Defaults to no.
show-unusable-uids
Show revoked and expired user IDs during signature verifica-
tion. Defaults to no.
pka-lookups
Enable PKA lookups to verify sender addresses. Note that PKA
is based on DNS, and so enabling this option may disclose
information on when and what signatures are verified or to whom
data is encrypted. This is similar to the "web bug" described
for the auto-key-retrieve feature.
pka-trust-increase
Raise the trust in a signature to full if the signature passes
PKA validation. This option is only meaningful if pka-lookups
is set.
--enable-dsa2
--disable-dsa2
Enables new-style DSA keys which (unlike the old style) may be larger
than 1024 bit and use hashes other than SHA-1 and RIPEMD/160. Note that
very few programs currently support these keys and signatures from them.
--show-photos
--no-show-photos
Causes --list-keys, --list-sigs, --list-public-keys, --list-secret-keys,
and verifying a signature to also display the photo ID attached to the
key, if any. See also --photo-viewer. These options are deprecated.
Use ‘--list-options [no-]show-photos’ and/or ‘--verify-options [no-]show-
photos’ instead.
--photo-viewer string
This is the command line that should be run to view a photo ID. "%i"
will be expanded to a filename containing the photo. "%I" does the same,
except the file will not be deleted once the viewer exits. Other flags
are "%k" for the key ID, "%K" for the long key ID, "%f" for the key fin-
gerprint, "%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 exe-
cuting it from GnuPG does not make it secure.
--exec-path string
Sets a list of directories to search for photo viewers and keyserver
helpers. If not provided, keyserver helpers use the compiled-in default
directory, and photo viewers use the $PATH environment variable. Note,
that on W32 system this value is ignored when searching for keyserver
helpers.
--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.
--keyring file
Add file to the current list of keyrings. If file begins with a tilde
and a slash, these are replaced by the $HOME directory. If the filename
does not contain a slash, it is assumed to be in the GnuPG home directory
("~/.gnupg" if --homedir or $GNUPGHOME is not used).
Note that this adds a keyring to the current list. If the intent is to
use the specified keyring alone, use --keyring along with --no-default-
keyring.
--secret-keyring file
Same as --keyring but for the secret keyrings.
--primary-keyring file
Designate file as the primary public keyring. This means that newly
imported keys (via --import or keyserver --recv-from) will go to this
keyring.
--trustdb-name file
Use file instead of the default trustdb. If file begins with a tilde and
a slash, these are replaced by the $HOME directory. If the filename does
not contain a slash, it is assumed to be in the GnuPG home directory
("~/.gnupg" if --homedir or $GNUPGHOME is not used).
--homedir directory
Set the name of the home directory to 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.
--pcsc-driver file
Use file to access the smartcard reader. The current default is ‘libpc-
sclite.so.1’ for GLIBC based systems, ‘/System/Library/Frame-
works/PCSC.framework/PCSC’ for MAC OS X, ‘winscard.dll’ for Windows and
‘libpcsclite.so’ for other systems.
--ctapi-driver file
Use file to access the smartcard reader. The current default is ‘libtow-
itoko.so’. Note that the use of this interface is deprecated; it may be
removed in future releases.
--disable-ccid
Disable the integrated support for CCID compliant readers. This allows
to fall back to one of the other drivers even if the internal CCID driver
can handle the reader. Note, that CCID support is only available if
libusb was available at build time.
--reader-port number_or_string
This option may be used to specify the port of the card terminal. A
value of 0 refers to the first serial device; add 32768 to access USB
devices. The default is 32768 (first USB device). PC/SC or CCID readers
might need a string here; run the program in verbose mode to get a list
of available readers. The default is then the first reader found.
--display-charset name
Set the name of the native character set. This is used to convert some
informational strings like user IDs to the proper UTF-8 encoding. Note
that this has nothing to do with the character set of data to be
encrypted or signed; GnuPG does not recode user supplied data. If this
option is not used, the default character set is determined from the cur-
rent locale. A verbosity level of 3 shows the chosen set. Valid values
for name are:
iso-8859-1
This is the Latin 1 set.
iso-8859-2
The Latin 2 set.
iso-8859-15
This is currently an alias for the Latin 1 set.
koi8-r The usual Russian set (rfc1489).
utf-8 Bypass all translations and assume that the OS uses native
UTF-8 encoding.
--utf8-strings
--no-utf8-strings
Assume that command line arguments are given as UTF8 strings. The
default (--no-utf8-strings) is to assume that arguments are encoded in
the character set as specified by --display-charset. These options affect
all following arguments. Both options may be used multiple times.
--options file
Read options from file and do not try to read them from the default
options file in the homedir (see --homedir). This option is ignored if
used in an options file.
--no-options
Shortcut for "--options /dev/null". This option is detected before an
attempt to open an option file. Using this option will also prevent the
creation of a "~./gnupg" homedir.
--load-extension name
Load an extension module. If 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.
--debug flags
Set debugging flags. All flags are or-ed and flags may be given in C syn-
tax (e.g. 0x0042).
--debug-all
Set all useful debugging flags.
--debug-ccid-driver
Enable debug output from the included CCID driver for smartcards. Note
that this option is only available on some system.
--enable-progress-filter
Enable certain PROGRESS status outputs. This option allows frontends to
display a progress indicator while gpg is processing larger files. There
is a slight performance overhead using it.
--status-fd n
Write special status strings to the file descriptor n. See the file
DETAILS in the documentation for a listing of them.
--status-file file
Same as --status-fd, except the status data is written to file file.
--logger-fd n
Write log output to file descriptor n and not to stderr.
--logger-file file
Same as --logger-fd, except the logger data is written to file file.
--attribute-fd n
Write attribute subpackets to the file descriptor n. This is most useful
for use with --status-fd, since the status messages are needed to sepa-
rate out the various subpackets from the stream delivered to the file
descriptor.
--attribute-file file
Same as --attribute-fd, except the attribute data is written to file
file.
--comment string
--no-comments
Use string as a comment string in clear text signatures and ASCII armored
messages or keys (see --armor). The default behavior is not to use a
comment string. --comment may be repeated multiple times to get multiple
comment strings. --no-comments removes all comments. It is a good idea
to keep the length of a single comment below 60 characters to avoid prob-
lems with mail programs wrapping such lines. Note that comment lines,
like all other header lines, are not protected by the signature.
--emit-version
--no-emit-version
Force inclusion of the version string in ASCII armored output. --no-
emit-version disables this option.
--sig-notation name=value
--cert-notation name=value
-N, --set-notation name=value
Put the name value pair into the signature as notation data. name must
consist only of printable characters or spaces, and must contain a ’@’
character in the form keyname AT domain.com (substituting the appro-
priate keyname and domain name, of course). This is to help prevent pol-
lution of the IETF reserved notation namespace. The --expert flag over-
rides the ’@’ check. value may be any printable string; it will be
encoded in UTF8, so you should check that your --display-charset is set
correctly. If you prefix name with an exclamation mark (!), the notation
data will be flagged as critical (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 finger-
print 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.
--show-notation
--no-show-notation
Show signature notations in the --list-sigs or --check-sigs listings as
well as when verifying a signature with a notation in it. These options
are deprecated. Use ‘--list-options [no-]show-notation’ and/or ‘--ver-
ify-options [no-]show-notation’ instead.
--sig-policy-url string
--cert-policy-url string
--set-policy-url string
Use 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 signa-
tures. --cert-policy-url sets a policy url for key signatures (certifi-
cations). --set-policy-url sets both.
The same %-expandos used for notation data are available here as well.
--show-policy-url
--no-show-policy-url
Show policy URLs in the --list-sigs or --check-sigs listings as well as
when verifying a signature with a policy URL in it. These options are
deprecated. Use ‘--list-options [no-]show-policy-url’ and/or ‘--verify-
options [no-]show-policy-url’ instead.
--sig-keyserver-url string
Use string as a preferred keyserver URL for data signatures. If you pre-
fix it with an exclamation mark, the keyserver URL packet will be flagged
as critical.
The same %-expandos used for notation data are available here as well.
--set-filename string
Use string as the filename which is stored inside messages. This over-
rides the default, which is to use the actual filename of the file being
encrypted.
--for-your-eyes-only
--no-for-your-eyes-only
Set the ‘for your eyes only’ flag in the message. This causes GnuPG to
refuse to save the file unless the --output option is given, and PGP to
use the "secure viewer" with a Tempest-resistant font to display the mes-
sage. This option overrides --set-filename. --no-for-your-eyes-only
disables this option.
--use-embedded-filename
--no-use-embedded-filename
Try to create a file with a name as embedded in the data. This can be a
dangerous option as it allows to overwrite files. Defaults to no.
--completes-needed n
Number of completely trusted users to introduce a new key signer
(defaults to 1).
--marginals-needed n
Number of marginally trusted users to introduce a new key signer
(defaults to 3)
--max-cert-depth n
Maximum depth of a certification chain (default is 5).
--cipher-algo name
Use name as cipher algorithm. Running the program with the command --ver-
sion yields a list of supported algorithms. If this is not used the
cipher algorithm is selected from the preferences stored with the key.
In general, you do not want to use this option as it allows you to vio-
late the OpenPGP standard. --personal-cipher-preferences is the safe way
to accomplish the same thing.
--digest-algo name
Use name as the message digest algorithm. Running the program with the
command --version yields a list of supported algorithms. In general, you
do not want to use this option as it allows you to violate the OpenPGP
standard. --personal-digest-preferences is the safe way to accomplish
the same thing.
--compress-algo name
Use compression algorithm name. "zlib" is RFC-1950 ZLIB compression.
"zip" is RFC-1951 ZIP compression which is used by PGP. "bzip2" is a
more modern compression scheme that can compress some things better than
zip or zlib, but at the cost of more memory used during compression and
decompression. "uncompressed" or "none" disables compression. If this
option is not used, the default behavior is to examine the recipient key
preferences to see which algorithms the recipient supports. If all else
fails, ZIP is used for maximum compatibility.
ZLIB may give better compression results than ZIP, as the compression
window size is not limited to 8k. BZIP2 may give even better compression
results than that, but will use a significantly larger amount of memory
while compressing and decompressing. This may be significant in low mem-
ory situations. Note, however, that PGP (all versions) only supports ZIP
compression. Using any algorithm other than ZIP or "none" will make the
message unreadable with PGP. In general, you do not want to use this
option as it allows you to violate the OpenPGP standard. --personal-com-
press-preferences is the safe way to accomplish the same thing.
--cert-digest-algo name
Use name as the message digest algorithm used when signing a key. Run-
ning 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.
--s2k-cipher-algo name
Use 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.
--s2k-digest-algo name
Use name as the digest algorithm used to mangle the passphrases. The
default algorithm is SHA-1.
--s2k-mode n
Selects how passphrases are mangled. If 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.
--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 appli-
cations 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).
--disable-cipher-algo name
Never allow the use of name as cipher algorithm. The given name will not
be checked so that a later loaded algorithm will still get disabled.
--disable-pubkey-algo name
Never allow the use of name as public key algorithm. The given name will
not be checked so that a later loaded algorithm will still get disabled.
--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.
--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 perfor-
mance penalty does not matter in most settings.
--auto-check-trustdb
--no-auto-check-trustdb
If GnuPG feels that its information about the Web of Trust has to be
updated, it automatically runs the --check-trustdb command internally.
This may be a time consuming process. --no-auto-check-trustdb disables
this option.
--throw-keyids
--no-throw-keyids
Do not put the recipient key IDs into encrypted messages. This helps to
hide the receivers of the message and is a limited countermeasure against
traffic analysis. On the receiving side, it may slow down the decryption
process because all available secret keys must be tried. --no-throw-
keyids disables this option. This option is essentially the same as
using --hidden-recipient for all recipients.
--not-dash-escaped
This option changes the behavior of cleartext signatures so that they can
be used for patch files. You should not send such an armored file via
email because all spaces and line endings are hashed too. You can not
use this option for data which has 5 dashes at the beginning of a line,
patch files don’t have this. A special armor header line tells GnuPG
about this cleartext signature option.
--escape-from-lines
--no-escape-from-lines
Because some mailers change lines starting with "From " to ">From " it is
good to handle such lines in a special way when creating cleartext signa-
tures to prevent the mail system from breaking the signature. Note that
all other PGP versions do it this way too. Enabled by default. --no-
escape-from-lines disables this option.
--passphrase-fd n
Read the passphrase from file descriptor n. Only the first line will be
read from file descriptor n. If you use 0 for n, the passphrase will be
read from stdin. This can only be used if only one passphrase is sup-
plied.
--passphrase-file file
Read the passphrase from file file. Only the first line will be read
from file file. This can only be used if only one passphrase is sup-
plied. Obviously, a passphrase stored in a file is of questionable secu-
rity if other users can read this file. Don’t use this option if you can
avoid it.
--passphrase string
Use string as the passphrase. This can only be used if only one
passphrase is supplied. Obviously, this is of very questionable security
on a multi-user system. Don’t use this option if you can avoid it.
--command-fd n
This is a replacement for the deprecated shared-memory IPC mode. If this
option is enabled, user input on questions is not expected from the TTY
but from the given file descriptor. It should be used together with
--status-fd. See the file doc/DETAILS in the source distribution for
details on how to use it.
--command-file file
Same as --command-fd, except the commands are read out of file file
--use-agent
--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.
--gpg-agent-info
Override the value of the environment variable GPG_AGENT_INFO. This is
only used when --use-agent has been given
Compliance options
These options control what GnuPG is compliant to. Only one of these
options may be active at a time. Note that the default setting of this
is nearly always the correct one. See the INTEROPERABILITY WITH OTHER
OPENPGP PROGRAMS section below before using one of these options.
--gnupg Use standard GnuPG behavior. This is essentially OpenPGP
behavior (see --openpgp), but with some additional workarounds
for common compatibility problems in different versions of PGP.
This is the default option, so it is not generally needed, but
it may be useful to override a different compliance option in
the gpg.conf file.
--openpgp Reset all packet, cipher and digest options to strict OpenPGP
behavior. Use this option to reset all previous options like
--rfc1991, --force-v3-sigs, --s2k-*, --cipher-algo, --digest-
algo and --compress-algo to OpenPGP compliant values. All PGP
workarounds are disabled.
--rfc2440 Reset all packet, cipher and digest options to strict RFC-2440
behavior. Note that this is currently the same thing as
--openpgp.
--rfc1991 Try to be more RFC-1991 (PGP 2.x) compliant.
--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.
--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 sign-
ing 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’
--pgp7 Set up all options to be as PGP 7 compliant as possible. This
is identical to --pgp6 except that MDCs are not disabled, and
the list of allowable ciphers is expanded to add AES128,
AES192, AES256, and TWOFISH.
--pgp8 Set up all options to be as PGP 8 compliant as possible. PGP 8
is a lot closer to the OpenPGP standard than previous versions
of PGP, so all this does is disable --throw-keyids and set
--escape-from-lines. All algorithms are allowed except for the
SHA224, SHA384, and SHA512 digests.
--force-v3-sigs
--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 expira-
tion dates. --no-force-v3-sigs disables this option.
--force-v4-certs
--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.
--force-mdc
Force the use of encryption with a modification detection code. This is
always used with the newer ciphers (those with a blocksize greater than
64 bits), or if all of the recipient keys indicate MDC support in their
feature flags.
--disable-mdc
Disable the use of the modification detection code. Note that by using
this option, the encrypted message becomes vulnerable to a message modi-
fication attack.
--allow-non-selfsigned-uid
--no-allow-non-selfsigned-uid
Allow the import and use of keys with user IDs which are not self-signed.
This is not recommended, as a non self-signed user ID is trivial to
forge. --no-allow-non-selfsigned-uid disables.
--allow-freeform-uid
Disable all checks on the form of the user ID while generating a new one.
This option should only be used in very special environments as it does
not ensure the de-facto standard format of user IDs.
--ignore-time-conflict
GnuPG normally checks that the timestamps associated with keys and signa-
tures have plausible values. However, sometimes a signature seems to be
older than the key due to clock problems. This option makes these checks
just a warning. See also --ignore-valid-from for timestamp issues on
subkeys.
--ignore-valid-from
GnuPG normally does not select and use subkeys created in the future.
This option allows the use of such keys and thus exhibits the pre-1.0.7
behaviour. You should not use this option unless you there is some clock
problem. See also --ignore-time-conflict for timestamp issues with sig-
natures.
--ignore-crc-error
The ASCII armor used by OpenPGP is protected by a CRC checksum against
transmission errors. Occasionally the CRC gets mangled somewhere on the
transmission channel but the actual content (which is protected by the
OpenPGP protocol anyway) is still okay. This option allows GnuPG to
ignore CRC errors.
--ignore-mdc-error
This option changes a MDC integrity protection failure into a warning.
This can be useful if a message is partially corrupt, but it is necessary
to get as much data as possible out of the corrupt message. However, be
aware that a MDC protection failure may also mean that the message was
tampered with intentionally by an attacker.
--lock-once
Lock the databases the first time a lock is requested and do not release
the lock until the process terminates.
--lock-multiple
Release the locks every time a lock is no longer needed. Use this to
override a previous --lock-once from a config file.
--lock-never
Disable locking entirely. This option should be used only in very spe-
cial environments, where it can be assured that only one process is
accessing those files. A bootable floppy with a stand-alone encryption
system will probably use this. Improper usage of this option may lead to
data and key corruption.
--exit-on-status-write-error
This option will cause write errors on the status FD to immediately ter-
minate the process. That should in fact be the default but it never
worked this way and thus we need an option to enable this, so that the
change won’t break applications which close their end of a status fd con-
nected pipe too early. Using this option along with --enable-progress-
filter may be used to cleanly cancel long running gpg operations.
--limit-card-insert-tries n
With n greater than 0 the number of prompts asking to insert a smartcard
gets limited to N-1. Thus with a value of 1 gpg won’t at all ask to
insert a card if none has been inserted at startup. This option is useful
in the configuration file in case an application does not know about the
smartcard support and waits ad infinitum for an inserted card.
--no-random-seed-file
GnuPG uses a file to store its internal random pool over invocations.
This makes random generation faster; however sometimes write operations
are not desired. This option can be used to achieve that with the cost
of slower random generation.
--no-verbose
Reset verbose level to 0.
--no-greeting
Suppress the initial copyright message.
--no-secmem-warning
Suppress the warning about "using insecure memory".
--no-permission-warning
Suppress the warning about unsafe file and home directory (--homedir)
permissions. Note that the permission checks that GnuPG performs are not
intended to be authoritative, but rather they simply warn about certain
common permission problems. Do not assume that the lack of a warning
means that your system is secure.
Note that the warning for unsafe --homedir permissions cannot be sup-
pressed in the gpg.conf file, as this would allow an attacker to place an
unsafe gpg.conf file in place, and use this file to suppress warnings
about itself. The --homedir permissions warning may only be suppressed
on the command line.
--no-mdc-warning
Suppress the warning about missing MDC integrity protection.
--require-secmem
--no-require-secmem
Refuse to run if GnuPG cannot get secure memory. Defaults to no (i.e.
run, but give a warning).
--no-armor
Assume the input data is not in ASCII armored format.
--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.
--skip-verify
Skip the signature verification step. This may be used to make the
decryption faster if the signature verification is not needed.
--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 for-
mat 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.
--with-key-data
Print key listings delimited by colons (like --with-colons) and print the
public key data.
--with-fingerprint
Same as the command --fingerprint but changes only the format of the out-
put and may be used together with another command.
--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.
--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.
--list-only
Changes the behaviour of some commands. This is like --dry-run but dif-
ferent 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.
--no-literal
This is not for normal use. Use the source to see for what it might be
useful.
--set-filesize
This is not for normal use. Use the source to see for what it might be
useful.
--show-session-key
Display the session key used for one message. See --override-session-key
for the counterpart of this option.
We think that Key Escrow is a Bad Thing; however the user should have the
freedom to decide whether to go to prison or to reveal the content of one
specific message without compromising all messages ever encrypted for one
secret key. DON’T USE IT UNLESS YOU ARE REALLY FORCED TO DO SO.
--override-session-key string
Don’t use the public key but the session key string. The format of this
string is the same as the one printed by --show-session-key. This option
is normally not used but comes handy in case someone forces you to reveal
the content of an encrypted message; using this option you can do this
without handing out the secret key.
--require-cross-certification
--no-require-certification
When verifying a signature made from a subkey, ensure that the cross cer-
tification "back signature" on the subkey is present and valid. This
protects against a subtle attack against subkeys that can sign. Cur-
rently defaults to --no-require-cross-certification, but will be changed
to --require-cross-certification in the future.
--ask-sig-expire
--no-ask-sig-expire
When making a data signature, prompt for an expiration time. If this
option is not specified, the expiration time set via --default-sig-expire
is used. --no-ask-sig-expire disables this option. Note that by
default, --force-v3-sigs is set which also disables this option. If you
want signature expiration, you must set --no-force-v3-sigs as well as
turning --ask-sig-expire on.
--default-sig-expire
The default expiration time to use for signature expiration. Valid val-
ues are "0" for no expiration, a number followed by the letter d (for
days), w (for weeks), m (for months), or y (for years) (for example "2m"
for two months, or "5y" for five years), or an absolute date in the form
YYYY-MM-DD. Defaults to "0".
--ask-cert-expire
--no-ask-cert-expire
When making a key signature, prompt for an expiration time. If this
option is not specified, the expiration time set via --default-cert-
expire is used. --no-ask-cert-expire disables this option.
--default-cert-expire
The default expiration time to use for key signature expiration. Valid
values are "0" for no expiration, a number followed by the letter d (for
days), w (for weeks), m (for months), or y (for years) (for example "2m"
for two months, or "5y" for five years), or an absolute date in the form
YYYY-MM-DD. Defaults to "0".
--expert
--no-expert
Allow the user to do certain nonsensical or "silly" things like signing
an expired or revoked key, or certain potentially incompatible things
like generating unusual key types. This also disables certain warning
messages about potentially incompatible actions. As the name implies,
this option is for experts only. If you don’t fully understand the
implications of what it allows you to do, leave this off. --no-expert
disables this option.
--allow-secret-key-import
This is an obsolete option and is not used anywhere.
--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.
--allow-multisig-verification
Allow verification of concatenated signed messages. This will run a sig-
nature verification for each data+signature block. There are some secu-
rity issues with this option and thus it is off by default. Note that
versions of GPG prior to version 1.4.3 implicitly allowed this.
--enable-special-filenames
This options enables a mode in which filenames of the form -&n, where n
is a non-negative decimal number, refer to the file descriptor n and not
to a file with that name.
--no-expensive-trust-checks
Experimental use only.
--group name=value1 [value2 value3 ...]
Sets up a named group, which is similar to aliases in email programs.
Any time the group name is a recipient (-r or --recipient), it will be
expanded to the values specified. Multiple groups with the same name are
automatically merged into a single group.
The values are key IDs or fingerprints, but any key description is
accepted. Note that a value with spaces in it will be treated as two
different values. Note also there is only one level of expansion - you
cannot make an group that points to another group. When used from the
command line, it may be necessary to quote the argument to this option to
prevent the shell from treating it as multiple arguments.
--ungroup name
Remove a given entry from the --group list.
--no-groups
Remove all entries from the --group list.
--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.
--personal-cipher-preferences string
Set the list of personal cipher preferences to 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.
--personal-digest-preferences string
Set the list of personal digest preferences to 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.
--personal-compress-preferences string
Set the list of personal compression preferences to 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).
--default-preference-list string
Set the list of default preferences to string. This preference list is
used for new keys and becomes the default for "setpref" in the edit menu.
--default-keyserver-url name
Set the default keyserver URL to name. This keyserver will be used as
the keyserver URL when writing a new self-signature on a key, which
includes key generation and changing preferences.
--list-config [names]
Display various internal configuration parameters of GnuPG. This option
is intended for external programs that call GnuPG to perform tasks, and
is thus not generally useful. See the file doc/DETAILS in the source
distribution for the details of which configuration items may be listed.
--list-config is only usable with --with-colons set.
How to specify a user ID
There are different ways to specify a user ID to GnuPG; here are some examples:
234567C4
0F34E556E
01347A56A
0xAB123456
Here the key ID is given in the usual short form.
234AABBCC34567C4
0F323456784E56EAB
01AB3FED1347A5612
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).
1234343434343434C434343434343434
123434343434343C3434343434343734349A3434
0E12343434343434343434EAB3484343434343434
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).
=Heinrich Heine <heinrichh AT uni-duesseldorf.de>
Using an exact to match string. The equal sign indicates this.
<heinrichh AT uni-duesseldorf.de>
Using the email address part which must match exactly. The left angle
bracket indicates this email address mode.
@heinrichh
Match within the <email.address> part of a user ID. The at sign indi-
cates this email address mode.
Heine
*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.
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.
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.
EXAMPLES
gpg -se -r Bob file
sign and encrypt for user Bob
gpg --clearsign file
make a clear text signature
gpg -sb file
make a detached signature
gpg --list-keys user_ID
show keys
gpg --fingerprint user_ID
show fingerprint
gpg --verify pgpfile
gpg --verify sigfile [files]
Verify the signature of the file but do not output the data. The second
form is used for detached signatures, where sigfile is the detached
signature (either ASCII armored or binary) and [files] are the signed
data; if this is not given, the name of the file holding the signed data
is constructed by cutting off the extension (".asc" or ".sig") of sigfile
or by asking the user for the filename.
ENVIRONMENT
HOME Used to locate the default home directory.
GNUPGHOME If set directory used instead of "~/.gnupg".
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.
COLUMNS
LINES Used to size some displays to the full size of the screen.
FILES
~/.gnupg/secring.gpg
The secret keyring
~/.gnupg/secring.gpg.lock
and the lock file
~/.gnupg/pubring.gpg
The public keyring
~/.gnupg/pubring.gpg.lock
and the lock file
~/.gnupg/trustdb.gpg
The trust database
~/.gnupg/trustdb.gpg.lock
and the lock file
~/.gnupg/random_seed
used to preserve the internal random pool
~/.gnupg/gpg.conf
Default configuration file
~/.gnupg/options
Old style configuration file; only used when gpg.conf is not found
/usr[/local]/share/gnupg/options.skel
Skeleton options file
/usr[/local]/lib/gnupg/
Default location for extensions
WARNINGS
Use a *good* password for your user account and a *good* passphrase to protect your
secret key. This passphrase is the weakest part of the whole system. Programs to
do dictionary attacks on your secret keyring are very easy to write and so you
should protect your "~/.gnupg/" directory very well.
Keep in mind that, if this program is used over a network (telnet), it is *very*
easy to spy out your passphrase!
If you are going to verify detached signatures, make sure that the program knows
about it; either give both filenames on the command line or use - to specify stdin.
INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS
GnuPG tries to be a very flexible implementation of the OpenPGP standard. In par-
ticular, GnuPG implements many of the optional parts of the standard, such as the
SHA-512 hash, and the ZLIB and BZIP2 compression algorithms. It is important to be
aware that not all OpenPGP programs implement these optional algorithms and that by
forcing their use via the --cipher-algo, --digest-algo, --cert-digest-algo, or
--compress-algo options in GnuPG, it is possible to create a perfectly valid
OpenPGP message, but one that cannot be read by the intended recipient.
There are dozens of variations of OpenPGP programs available, and each supports a
slightly different subset of these optional algorithms. For example, until
recently, no (unhacked) version of PGP supported the BLOWFISH cipher algorithm. A
message using BLOWFISH simply could not be read by a PGP user. By default, GnuPG
uses the standard OpenPGP preferences system that will always do the right thing
and create messages that are usable by all recipients, regardless of which OpenPGP
program they use. Only override this safe default if you really know what you are
doing.
If you absolutely must override the safe default, or if the preferences on a given
key are invalid for some reason, you are far better off using the --pgp6, --pgp7,
or --pgp8 options. These options are safe as they do not force any particular
algorithms in violation of OpenPGP, but rather reduce the available algorithms to a
"PGP-safe" list.
BUGS
On 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.
gpg(1)
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