gpg
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 documentation get the GNU Privacy Handbook (GPH) or one of the
other documents at http://www.gnupg.org/docs.html .
Please remember that option parsing stops as soon as a non option is
encountered, you can explicitly stop option parsing by using the spe-
cial option "--".
COMMANDS
gpg recognizes these commands:
-s, --sign
Make a signature. This command may be combined with
--encrypt.
--clearsign
Make a clear text signature.
-b, --detach-sign
Make a detached signature.
-e, --encrypt
Encrypt data. This option may be combined with --sign.
-c, --symmetric
Encrypt with symmetric cipher only. This command asks for a
passphrase.
--store Store only (make a simple RFC1991 packet).
--decrypt [file]
Decrypt file (or stdin if no file is specified) and write it
to stdout (or the file specified with --output). If the
decrypted file is signed, the signature is also verified.
This command differs from the default operation, as it never
writes to the filename which is included in the file and it
rejects files which don't begin with an encrypted message.
--verify [[sigfile] [signed-files]]
Assume that sigfile is a signature and verify it without gen-
erating 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 filename. For security reasons a detached sig-
nature cannot read the signed material from stdin without
denoting it in the above way.
--verify-files [files]
This is a special version of the --verify command which does
not work with detached signatures. The command expects the
files to be verified either on the command line or reads the
filenames from stdin; each name must be on separate line.
The command is intended for quick checking of many files.
--encrypt-files [files]
This is a special version of the --encrypt command. The com-
mand expects the files to be encrypted either on the command
line or reads the filenames from stdin; each name must be on
separate line. The command is intended for a quick encryption
of multiple files.
--decrypt-files [files]
The same as --encrypt-files with the difference that files
will be decrypted. The syntax or the filenames is the same.
--list-keys [names]
--list-public-keys [names]
List all keys from the public keyrings, or just the ones
given on the command line.
--list-secret-keys [names]
List all keys from the secret keyrings, or just the ones
given on the command line. 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.
--check-sigs [names]
Same as --list-sigs, but the signatures are verified.
--fingerprint [names]
List all keys with their fingerprints. This is the same out-
put 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 finger-
prints 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
interactively.
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 informa-
tion of the key again, together with its finger-
print 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 oth-
ers. 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.
nrlsign Combines the functionality of nrsign and lsign to
make a signature that is both non-revocable and
non-exportable.
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.
trust Change the owner trust value. This updates the
trust-db immediately and no save is required.
disable
enable Disable or enable an entire key. A disabled key can
normally not be used for encryption.
adduid Create an alternate user id.
addphoto Create a photographic user id.
deluid Delete a user id.
addkey Add a subkey to this key.
delkey Remove a subkey.
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).
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 selection, 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 primary user id flag from all other
user ids and sets the timestamp of all affected
self-signatures one second ahead. Note that set-
ting 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 reg-
ular 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 preference
list.
setpref string
Set the list of user ID preferences to 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 set the pref-
erences to nil. Use "gpg -v --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.
updpref Change the preferences of all user IDs (or just of
the selected ones to the current list of prefer-
ences. The timestamp of all affected self-signa-
tures 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 prefer-
ences will not be used by GnuPG.
toggle Toggle between public and secret key listing.
save Save all changes to the key rings and quit.
quit Quit the program without updating the key rings.
The listing shows you the key with its secondary keys and all
user ids. Selected keys or user ids 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.
--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.
--nrsign-key name
Signs a public key with your secret key but marks it as non-
revocable. This is a shortcut version of the subcommand
"nrsign" 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 finger-
print. This is a safeguard 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
Generate a revocation certificate for the complete key. To
revoke a subkey or a signature, use the --edit command.
--desig-revoke
Generate a designated revocation certificate for a key. This
allows a user (with the permission of the keyholder) to
revoke someone elses key.
--export [names]
Either export all keys from all keyrings (default keyrings
and those registered via option --keyring), or if at least
one name is given, those of the given name. The new keyring
is written to stdout or to the file given with option "out-
put". 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-all [names]
Same as --export, but also exports keys which are not compat-
ible with OpenPGP.
--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 useless; this is a GNU exten-
sion 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 --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 --keyserver must be used to give the name of this key-
server.
--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. Option --keyserver
must be used to give the name of this keyserver.
--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.
--update-trustdb
Do trust DB maintenance. This command goes over all keys and
builds the Web-of-Trust. This is an interactive command
because it may has to ask for the "ownertrust" values of
keys. The user has to give an estimation in how far she
trusts the owner of the displayed key to correctly certify
(sign) other keys. It does only ask for that value if it has
not yet been assigned to a key. Using the edit menu, that
value can be changed at any time later.
--check-trustdb
Do trust DB maintenance without user interaction. Form time
to time the trust database must be updated so that expired
keys and resulting changes in the Web-of-Trust can be
tracked. GnuPG tries to figure when this is required and
then does it implicitly; this command can be used to force
such a check. The processing is identically 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 check is only done when it is
due. To force a run even in batch mode add the option --yes.
--export-ownertrust [file]
Store the ownertrust values into file (or stdin if not
given). This is useful for backup purposes as these values
are the only ones which can't be re-created from a corrupted
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 situations 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 available 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.
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 does not make sense.
gpg recognizes these options:
-a, --armor
Create ASCII armored output.
-o, --output file
Write output to file.
-u, --local-user name
Use name as the user ID to sign. This option is silently
ignored for the list commands, so that it can be used in an
options file.
--default-key name
Use name as default user ID for signatures. If this is not
used the default user ID is the first user ID found in the
secret keyring.
-r, --recipient name
Encrypt for user id name. If this option 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 --recipi-
ent 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.
--no-encrypt-to
Disable the use of all --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 n
Set compression level to n. A value of 0 for n disables com-
pression. Default is to use the default compression level of
zlib (normally 6).
-t, --textmode
Use canonical text mode. If -t (but not --textmode) is used
together with armoring and signing, this enables clearsigned
messages. This kludge is needed for PGP compatibility; nor-
mally you would use --sign or --clearsign to selected 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 Use batch mode. Never ask, do not allow interactive com-
mands.
--no-tty Make sure that the TTY (terminal) is never used for any out-
put. This option is needed in some cases because GnuPG some-
times prints warnings to the TTY if --batch is used.
--no-batch
Disable batch mode. This may be of use if --batch is enabled
from an options file.
--yes Assume "yes" on most questions.
--no Assume "no" on most questions.
--default-cert-check-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 exam-
ple, 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.
--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 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.
--always-trust
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.
--keyserver name
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:[//]keyserver-
name[:port]' The scheme is the type of keyserver: "hkp" for
the Horowitz (or compatible) keyservers, "ldap" for the NAI
LDAP keyserver, or "mailto" for the Horowitz 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 gen-
erally no need to send keys to more than one server. Using
the command "host -l pgp.net | grep wwwkeys" gives you a list
of HKP keyservers. When using one of the wwwkeys servers,
due to load balancing using round-robin DNS you may notice
that you get a different key server each time.
--keyserver-options 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 key-
server. While not all options are available for all key-
server types, some common options are:
include-revoked
When searching for a key, include keys that are
marked on the keyserver as revoked. Note that this
option is always set when using the NAI HKP key-
server, as this keyserver does not differentiate
between revoked and unrevoked keys. When using the
LDAP keyserver, this applies to both searching
(--search-keys) and receiving (--recv-keys).
include-disabled
When receiving or searching for a key, include keys
that are marked on the keyserver as disabled. Note
that this option is not used with HKP keyservers,
as they do not support disabling keys.
include-subkeys
When receiving a key, include subkeys in the
search. 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 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.
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 read-
ing the temporary files.
verbose Tell the keyserver helper program to be more ver-
bose. This option can be repeated multiple times
to increase the verbosity level.
honor-http-proxy
For keyserver schemes that use HTTP (such as HKP),
try to access the keyserver over the proxy set with
the environment variable "http_proxy".
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.
--import-options 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:
allow-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-hkp-subkey-bug
During import, attempt to repair the HKP keyserver
mangling multiple subkeys bug. Note that this can-
not completely repair the damaged key as some cru-
cial 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.
--export-options 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:
include-non-rfc
Include non-RFC compliant keys in the export.
Defaults to yes.
include-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.
include-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.
include-sensitive-revkeys
Include designated revoker information that was
marked as "sensitive". Defaults to 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.
--no-show-photos
Resets the --show-photos flag.
--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 finger-
print, "%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"
--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.
--show-keyring
Causes --list-keys, --list-public-keys, and --list-secret-
keys to display the name of the keyring a given key resides
on. This is only useful when you're listing a specific key or
set of keys. It has no effect when listing all keys.
--keyring file
Add file to the list of keyrings. If file begins with a
tilde and a slash, these are replaced by the HOME directory.
If the filename does not contain a slash, it is assumed to be
in the home-directory ("~/.gnupg" if --homedir is not used).
The filename may be prefixed with a scheme:
"gnupg-ring:" is the default one.
It might make sense to use it together with --no-default-
keyring.
--secret-keyring file
Same as --keyring but for the secret keyrings.
--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".
--charset name
Set the name of the native character set. This is used to
convert some strings to 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 used one.
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 the arguments are already given as UTF8 strings.
The default (--no-utf8-strings) is to assume that arguments
are encoded in the character set as specified by --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 dep-
recated.
--debug flags
Set debugging flags. All flags are or-ed and flags may be
given in C syntax (e.g. 0x0042).
--debug-all
Set all useful debugging flags.
--status-fd n
Write special status strings to the file descriptor n. See
the file DETAILS in the documentation for a listing of them.
--logger-fd n
Write log output to file descriptor n and not to stderr.
--attribute-fd n
Write attribute subpackets to the file descriptor n. This is
most useful for use with --status-fd, since the status mes-
sages are needed to separate out the various subpackets from
the stream delivered to the file descriptor.
--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
Resets the --sk-comments option.
--no-comment
See --sk-comments. This option is deprecated and may be
removed soon.
--comment string
Use string as comment string in clear text signatures. The
default is not do write a comment string.
--default-comment
Force to write the standard comment string in clear text sig-
natures. Use this to overwrite a --comment from a config
file. This option is now obsolete because there is no
default comment string anymore.
--no-version
Omit the version string in clear text signatures.
--emit-version
Force to write the version string in clear text signatures.
Use this to overwrite a previous --no-version from a config
file.
-N, --notation-data name=value
Put the name value pair into the signature as notation data.
name must consist only of alphanumeric characters, digits or
the underscore; the first character must not be a digit.
value may be any printable string; it will be encoded in
UTF8, so you should check that your --charset is set cor-
rectly. If you prefix name with an exclamation mark, the
notation data will be flagged as critical (rfc2440:5.2.3.15).
--show-notation
Show key signature notations in the --list-sigs or --check-
sigs listings.
--no-show-notation
Do not show key signature notations in the --list-sigs or
--check-sigs listings.
--set-policy-url string
Use string as 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.
--show-policy-url
Show any policy URLs set in the --list-sigs or --check-sigs
listings.
--no-show-policy-url
Do not show any policy URLs set in the --list-sigs or
--check-sigs listings.
--set-filename string
Use string as the name of file which is stored in messages.
--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
Resets the --for-your-eyes-only flag.
--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.
--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 --version yields a list of supported algorithms. If
this is not used the cipher algorithm is selected from the
preferences stored with the key.
--digest-algo name
Use name as the message digest algorithm. Running the program
with the command --version yields a list of supported algo-
rithms.
--cert-digest-algo name
Use 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 implementa-
tions 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 --cipher-algo is not given.
--s2k-digest-algo name
Use name as the digest algorithm used to mangle the
passphrases. The default algorithm is RIPE-MD-160. This
digest algorithm is also used for conventional encryption if
--digest-algo is not given.
--s2k-mode n
Selects how passphrases are mangled. If n is 0 a plain
passphrase (which is not recommended) will be used, a 1
(default) adds a salt to the passphrase and a 3 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 check-
sum. This method will be part of an enhanced OpenPGP speci-
fication 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 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 hap-
pen is to change the passphrase on the key (even changing it
to the same value is acceptable).
--compress-algo n
Use compression algorithm n. Default is 2 which is RFC1950
compression. You may use 1 to use the old zlib version
(RFC1951) which is used by PGP. 0 disables compression. The
default algorithm may give better results because the window
size is not limited to 8K. If this is not used the OpenPGP
behavior is used, i.e. the compression algorithm is selected
from the preferences; note, that this can't be done if you do
not encrypt the data.
--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 algo-
rithm 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 dis-
able 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 performance
penalty does not matter in most settings.
--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
Resets the --auto-check-trustdb option.
--throw-keyid
Do not put the keyid into encrypted packets. This option
hides the receiver of the message and is a countermeasure
against traffic analysis. It may slow down the decryption
process because all available secret keys are tried.
--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
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. All other PGP versions do
it this way too. This option is not enabled by default
because it would violate rfc2440.
--passphrase-fd n
Read the passphrase from file descriptor n. If you use 0 for
n, the passphrase will be read from stdin. This can
only be used if only one passphrase is supplied. Don't use
this option if you can avoid it.
--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.
--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.
--gpg-agent-info
Override the value of the environment variable
GPG_AGENT_INFO. This is only used when --use-agent has been
given
--rfc1991 Try to be more RFC1991 (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 --no-openpgp --disable-mdc
--no-force-v4-certs --no-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 dis-
ables --textmode when encrypting.
--no-pgp2 Resets the --pgp2 option.
--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 making signatures with signing subkeys as PGP 6
does not understand signatures made by signing subkeys.
This option implies `--disable-mdc --no-comment --escape-
from-lines --force-v3-sigs --no-ask-sig-expire --compress-
algo 1'
--no-pgp6 Resets the --pgp6 option.
--pgp7 Set up all options to be as PGP 7 compliant as possible.
This is identical to --pgp6 except that MDCs are not dis-
abled, and the list of allowable ciphers is expanded to add
AES128, AES192, AES256, and TWOFISH.
--no-pgp7 Resets the --pgp7 option.
--openpgp Reset all packet, cipher and digest options to OpenPGP behav-
ior. 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 also disabled.
--force-v3-sigs
OpenPGP states that an implementation should generate v4 sig-
natures but PGP versions 5 and higher only recognize v4 sig-
natures 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
Reset the --force-v3-sigs option.
--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
Reset the --force-v4-certs 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 the recipient key
has one of those ciphers as a preference.
--disable-mdc
Disable the use of the modification detection code. Note
that by using this option, the encrypted message becomes vul-
nerable to a message modification attack.
--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
Reset the --allow-non-selfsigned-uid option.
--allow-freeform-uid
Disable all checks on the form of the user ID while generat-
ing a new one. This option should only be used in very spe-
cial 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 signatures have plausible values. However, some-
times a signature seems to be older than the key due to clock
problems. This option makes these checks just a warning.
--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.
--ignore-crc-error
The ASCII armor used by OpenPGP is protected by a CRC check-
sum against transmission errors. Sometimes it happens that
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 will let gpg
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 cor-
rupt, but it is necessary to get as much data as possible out
of the corrupt message. However, be aware that a MDC protec-
tion 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 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 cor-
ruption.
--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 gener-
ation.
--no-verbose
Reset verbose level to 0.
--no-greeting
Suppress the initial copyright message but do not enter batch
mode.
--no-secmem-warning
Suppress the warning about "using insecure memory".
--no-permission-warning
Suppress the warning about unsafe file permissions.
--no-mdc-warning
Suppress the warning about missing MDC integrity protection.
--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.
--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 out-
put will be encoded in UTF-8 regardless of any --charset set-
ting.
--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 output 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 list-
ing. The exact behaviour of this option may change in future
versions.
--fixed-list-mode
Do not merge 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 different in some cases. The semantic of this com-
mand may be extended in the future. Currently it only skips
the actual decryption pass and therefore enables a fast list-
ing 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.
--emulate-md-encode-bug
GnuPG versions prior to 1.0.2 had a bug in the way a signa-
ture was encoded. This options enables a workaround by
checking faulty signatures again with the encoding used in
old versions. This may only happen for ElGamal signatures
which are not widely used.
--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 compro-
mising 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.
--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
Resets the --ask-sig-expire option.
--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
Resets the --ask-cert-expire option.
--expert Allow the user to do certain nonsensical or "silly" things
like signing an expired or revoked key, or certain poten-
tially incompatible things like generating deprecated 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
Resets the --expert option.
--merge-only
Don't insert new keys into the keyrings while doing an
import.
--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-keyid) and might come handy in case
where an encrypted message contains a bogus key ID.
--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 receipient (-r or
--recipient), it will be expanded to the values specified.
The values are key IDs or fingerprints, but any key descrip-
tion 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.
--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.
--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.
--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.
--default-preference-list string
Set the list of default preferences to 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.
How to specify a user ID
There are different ways on how 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@uni-duesseldorf.de>
Using an exact to match string. The equal sign indicates
this.
<heinrichh@uni-duesseldorf.de>
Using the email address part which must match exactly. The
left angle bracket indicates this email address mode.
+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.
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 finger-
prints. This flag tells GnuPG to use exactly the given primary or sec-
ondary key and not to try to figure out which secondary or primary 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 sig-
file is the detached signature (either ASCII armored of
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.
http_proxy
Only honored when the keyserver-option honor-http-proxy is
set.
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 pro-
gram knows about it; either be giving both filenames on the command
line or using - to specify stdin.
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 to disk. If you get no warn-
ing message about insecure memory your operating system supports lock-
ing without being root. The program drops root privileges as soon as
locked memory is allocated.
gpg(1)
