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/documentation/ .
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 may be run with no commands, in which case it will perform a rea-
sonable action depending on the type of file it is given as input (an
encrypted message is decrypted, a signature is verified, a file con-
taining 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 symmetrically 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 symmetric cipher used is CAST5, but may be chosen
with the --cipher-algo option. This option may be combined
with --sign (for a signed and symmetrically encrypted mes-
sage), --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 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 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 processing on the command line or read from stdin with
each filename on a separate line. This allows for many files
to be processed at once. --multifile may currently be used
along with --verify, --encrypt, and --decrypt. Note that
‘--multifile --verify’ may not be used with detached signa-
tures.
--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 infor-
mation about each signature. From left to right, they are
the numbers 1-3 for certificate check level (see --ask-cert-
level), "L" for a local or non-exportable signature (see
--lsign-key), "R" for a nonRevocable signature (see the
--edit-key command "nrsign"), "P" for a signature that con-
tains 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 signa-
ture 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 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.
tsign Make a trust signature. This is a signature that
combines the notions of certification (like a regu-
lar signature), and trust (like the "trust" com-
mand). 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 pre-
fixed to "sign" to create a signature of any type desired.
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
not normally 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 pro-
grams 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 cer-
tain 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 dur-
ing 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 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
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 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. 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 set-
pref 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 algo-
rithms. Note that while you can change the prefer-
ences 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 exist-
ing 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 nota-
tions, setting a notation prefixed with a minus
sign (-) removes that notation, and setting a nota-
tion 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 sub-
keys that may not currently have them. Cross-cer-
tification signatures protect 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/howtos.html#GnuPG-card-
HOWTO .
--card-status
Show the content of the smart card.
--change-pin
Present a menu to allow changing the PIN of a smartcard.
This functionality 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 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 name
Generate a revocation certificate for the complete key. To
revoke a subkey 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 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-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 --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 --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. Calling this with no
arguments will refresh the entire keyring. Option --key-
server must be used to give the name of the keyserver 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 key-
server types support different search methods. Currently
only LDAP supports them all.
--fetch-keys URIs
Retrieve keys located at the specified URIs. Note that dif-
ferent installations 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" val-
ues for keys. The user has to give an estimation of how far
she trusts the owner of the displayed key to correctly cer-
tify (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 signatures and the resulting changes in the
Web of Trust can be tracked. Normally, GnuPG will calculate
when this is required and do it automatically unless --no-
auto-check-trustdb is set. This command can be used to force
a trust database check at any time. The processing is iden-
tical to that of --update-trustdb but it skips keys with a
not yet defined "ownertrust".
For use with cron jobs, this command can be used together
with --batch in which case the trust database check is done
only if a check is needed. To force a run even in batch mode
add the option --yes.
--export-ownertrust
Send the ownertrust values to stdout. This is useful for
backup purposes as these values are the only ones which can’t
be re-created from a corrupted trust DB.
--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. For every option, con-
sult 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 compression, it is possible that the plain-
text of a given message may be significantly larger than the
original OpenPGP message. While GnuPG works properly with
such messages, there is often a desire to set a maximum file
size that will be generated before processing is forced to
stop by the OS limits. Defaults to 0, which means "no
limit".
--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-recipi-
ent 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 countermeasure 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 --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.
--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 compression algorithm
(defaulting to 6 as well). This is a different option from
--compress-level since BZIP2 uses a significant amount of
memory for each additional compression level. -z sets both.
A value of 0 for 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 plat-
forms 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 ver-
sions 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 com-
mands. --no-batch disables this option.
--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.
--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 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 (no particular claim).
--min-cert-level
When building the trust database, treat any signatures with a
certification 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 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.
--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 signa-
tures 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 earlier.
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 "[uncer-
tain]" 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 depre-
cated.
--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@example.com" form), and there are no
user@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.josefs-
son.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 --key-
server option may be used here to query that par-
ticular 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:[//]keyserver-
name[: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 particular installation of GnuPG may have other
keyserver types available as well. Keyserver schemes are
case-insensitive. After the keyserver name, optional key-
server 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 gen-
erally no need to send keys to more than one server. The
keyserver "hkp://subkeys.pgp.net" uses round robin DNS to
give a different keyserver each time you use it.
--keyserver-options name=value1 [value2 value3 ...]
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 with --search-keys,
include keys that are marked on the keyserver as
revoked. Note that not all keyservers differenti-
ate between revoked and unrevoked keys, and for
such keyservers this option is meaningless. Note
also that most keyservers do not have cryptographic
verification of key revocations, and so turning
this option off may result in skipping keys that
are incorrectly marked as revoked.
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 behav-
ior possible. Keyserver operators can see which
keys you request, so by sending you a message
signed by a brand new key (which you naturally will
not have on your local keyring), the operator can
tell both your IP address and the time when you
verified the signature.
honor-keyserver-url
When using --refresh-keys, if the key in question
has a preferred keyserver URL, then use that pre-
ferred keyserver to refresh the key from. In addi-
tion, if auto-key-retrieve is set, and the signa-
ture 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 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.
timeout[=value]
Tell the keyserver helper program how long (in sec-
onds) 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 com-
mand 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 specified, 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 importing 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 multiple subkeys. Note that this
cannot completely repair the damaged key as some
crucial data is removed by the keyserver, but it
does at least give you back one subkey. Defaults
to no for regular --import and to yes for keyserver
--recv-keys.
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 exporting 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 "sensitive". 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 unattended 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 modi-
fied. 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 list-
ings. 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 listings. 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 list-
ings 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 signature. 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 verified. 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
verification. 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 sig-
nature 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 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". Note that if your image viewer program is not
secure, then executing 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 depre-
cated: 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 direc-
tory. 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 ‘libpcsclite.so.1’ for GLIBC based systems, ‘/Sys-
tem/Library/Frameworks/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 ‘libtowitoko.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 ter-
minal. 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 read-
ers. 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 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.
--debug-ccid-driver
Enable debug output from the included CCID driver for smart-
cards. 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 pro-
cessing 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 mes-
sages are needed to separate 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 problems with mail programs wrapping such lines. Note
that comment lines, like all other header lines, are not pro-
tected by the signature.
--emit-version
--no-emit-version
Force inclusion of the version string in ASCII armored out-
put. --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@domain.exam-
ple.com (substituting the appropriate keyname and domain
name, of course). This is to help prevent pollution 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 --dis-
play-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
fingerprint of the key making the signature (which might be a
subkey), "%p" into the fingerprint of the primary key of the
key making the signature, "%c" into the signature count from
the OpenPGP smartcard, and "%%" results in a single "%". %k,
%K, and %f are only meaningful when making a key signature
(certification), and %c is only meaningful when using the
OpenPGP smartcard.
--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 nota-
tion in it. These options are deprecated. Use ‘--list-
options [no-]show-notation’ and/or ‘--verify-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 signatures. --cert-policy-url sets a
policy url for key signatures (certifications). --set-pol-
icy-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-pol-
icy-url’ instead.
--sig-keyserver-url string
Use string as a preferred keyserver URL for data signatures.
If you prefix it with an exclamation mark, the keyserver URL
packet will be flagged as critical.
The same %-expandos used for notation data are available here
as well.
--set-filename string
Use string as the filename which is stored inside messages.
This overrides the default, which is to use the actual file-
name 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 message. 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 --version 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 violate 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 algo-
rithms. 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 com-
pression. "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 recipi-
ent supports. If all else fails, ZIP is used for maximum
compatibility.
ZLIB may give better compression results than ZIP, as the
compression window size is not limited to 8k. BZIP2 may give
even better compression results than that, but will use a
significantly larger amount of memory while compressing and
decompressing. This may be significant in low memory situa-
tions. 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 gen-
eral, you do not want to use this option as it allows you to
violate the OpenPGP standard. --personal-compress-prefer-
ences 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. 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 --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 check-
sum. This method is part of the upcoming enhanced OpenPGP
specification but GnuPG already uses it as a countermeasure
against certain attacks. Old applications don’t understand
this new format, so this option may be used to switch back to
the old behaviour. Using this option bears a security risk.
Note that using this option only takes effect when the secret
key is encrypted - the simplest way to make this happen is to
change the passphrase on the key (even changing it to the
same value is acceptable).
--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
--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 lim-
ited countermeasure against traffic analysis. On the receiv-
ing side, it may slow down the decryption process because all
available secret keys must be tried. --no-throw-keyids dis-
ables 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 signatures to prevent the mail system
from breaking the signature. Note that all other PGP ver-
sions 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 supplied.
--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 supplied. Obviously, a passphrase stored in a
file is of questionable security 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 ques-
tionable 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 cur-
rently 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 --com-
press-algo 1’. It also disables --textmode when
encrypting.
--pgp6 Set up all options to be as PGP 6 compliant as pos-
sible. This restricts you to the ciphers IDEA (if
the IDEA plugin is installed), 3DES, and CAST5, the
hashes MD5, SHA1 and RIPEMD160, and the compression
algorithms none and ZIP. This also disables
--throw-keyids, and making signatures with signing
subkeys as PGP 6 does not understand signatures
made by signing subkeys.
This option implies ‘--disable-mdc --no-sk-comment
--escape-from-lines --force-v3-sigs --no-ask-sig-
expire’
--pgp7 Set up all options to be as PGP 7 compliant as pos-
sible. 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 pos-
sible. PGP 8 is a lot closer to the OpenPGP stan-
dard 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 sig-
natures but PGP versions 5 through 7 only recognize v4 signa-
tures on key material. This option forces v3 signatures for
signatures on data. Note that this option overrides --ask-
sig-expire, as v3 signatures cannot have expiration dates.
--no-force-v3-sigs disables this option.
--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 vul-
nerable to a message modification 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 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.
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 signatures.
--ignore-crc-error
The ASCII armor used by OpenPGP is protected by a CRC check-
sum 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 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.
--exit-on-status-write-error
This option will cause write errors on the status FD to imme-
diately terminate 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 appli-
cations which close their end of a status fd connected pipe
too early. Using this option along with --enable-progress-
filter may be used to cleanly cancel long running gpg opera-
tions.
--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 sup-
port 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 gener-
ation.
--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 prob-
lems. 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 suppressed 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 format is useful when GnuPG is called from
scripts and other programs as it is easily machine parsed.
The details of this format are documented in the file
doc/DETAILS, which is included in the GnuPG source distribu-
tion.
--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 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 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.
--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.
--require-cross-certification
--no-require-certification
When verifying a signature made from a subkey, ensure that
the cross certification "back signature" on the subkey is
present and valid. This protects against a subtle attack
against subkeys that can sign. Currently 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 expi-
ration, 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 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".
--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 expira-
tion. Valid values are "0" for no expiration, a number fol-
lowed 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 poten-
tially 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 implica-
tions 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 signature verification for each data+signature
block. There are some security 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 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. 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 encryp-
tion 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 with-
out 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 recipi-
ent keys to consider (e.g. --symmetric).
--default-preference-list string
Set the list of default preferences to string. This prefer-
ence 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-signa-
ture 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@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.
@heinrichh
Match within the <email.address> part of a user ID. The at
sign indicates 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 finger-
prints. This flag tells GnuPG to use the specified primary or sec-
ondary 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 sig-
file 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 con-
structed 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 pro-
gram 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 stan-
dard. In particular, GnuPG implements many of the optional parts of
the standard, such as the SHA-512 hash, and the ZLIB and BZIP2 compres-
sion algorithms. It is important to be aware that not all OpenPGP pro-
grams implement these optional algorithms and that by forcing their use
via the --cipher-algo, --digest-algo, --cert-digest-algo, or --com-
press-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 mes-
sages 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 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)
