GPG(1) GNU Privacy Guard GPG(1)
NAME
gpg - OpenPGP encryption and signing tool
SYNOPSIS
gpg [--homedir dir] [--options file] [options] command [args]
DESCRIPTION
gpg is the OpenPGP part of the GNU Privacy Guard (GnuPG). It is a tool
to provide digital encryption and signing services using the OpenPGP
standard. gpg features complete key management and all bells and whis
tles you can expect from a decent OpenPGP implementation.
This is the standalone version of gpg. For desktop use you should con
sider using gpg2.
COMMANDS
Commands are not distinguished from options execpt for the fact that
only one command is allowed.
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).
Please remember that option as well as command parsing stops as soon as
a non-option is encountered, you can explicitly stop parsing by using
the special option --.
Commands not specific to the function
--version
Print the program version and licensing information. Note that
you cannot abbreviate this command.
--help
-h Print a usage message summarizing the most useful command line
options. Not that you cannot abbreviate this command.
--warranty
Print warranty information.
--dump-options
Print a list of all available options and commands. Note that
you cannot abbreviate this command.
Commands to select the type of operation
--sign
-s 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 --symmet
ric together (for a signed message that may be decrypted via a
secret key or a passphrase).
--clearsign
Make a clear text signature. The content in a clear text signa
ture 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.
--detach-sign
-b Make a detached signature.
--encrypt
-e 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).
--symmetric
-c Encrypt with a symmetric cipher using a passphrase. The default
symmetric cipher used is CAST5, but may be chosen with the
--cipher-algo option. This option may be combined with --sign
(for a signed and symmetrically encrypted message), --encrypt
(for a message that may be decrypted via a secret key or a
passphrase), or --sign and --encrypt together (for a signed mes
sage that may be decrypted via a secret key or a passphrase).
--store
Store only (make a simple RFC1991 literal data packet).
--decrypt
-d Decrypt the file given on the command line (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 dont begin with an encrypted mes
sage.
--verify
Assume that the first argument is a signed file or a detached
signature and verify it without generating any output. With no
arguments, the signature packet is read from stdin. If only a
sigfile is given, it may be a complete signature or a detached
signature, in which case the signed stuff is expected in a file
without the ".sig" or ".asc" extension. With more than 1 argu
ment, 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 signa
ture 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 --ver
ify may not be used with detached signatures.
--verify-files
Identical to --multifile --verify.
--encrypt-files
Identical to --multifile --encrypt.
--decrypt-files
Identical to --multifile --decrypt.
--list-keys
-k
--list-public-keys
List all keys from the public keyrings, or just the keys given
on the command line. -k is slightly different from --list-keys
in that it allows only for one argument and takes the second
argument as the keyring to search. This is for command line
compatibility with PGP 2 and has been removed in gpg2.
Avoid using the output of this command in scripts or other pro
grams 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.
--list-secret-keys
-K 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
Same as --list-keys, but the signatures are listed too.
For each signature listed, there are several flags in between
the "sig" tag and keyid. These flags give additional information
about each signature. From left to right, they are the numbers
1-3 for certificate check level (see --ask-cert-level), "L" for
a local or non-exportable signature (see --lsign-key), "R" for a
nonRevocable signature (see the --edit-key command "nrsign"),
"P" for a signature that contains a policy URL (see --cert-pol
icy-url), "N" for a signature that contains a notation (see
--cert-notation), "X" for an eXpired signature (see --ask-cert-
expire), and the numbers 1-9 or "T" for 10 and above to indicate
trust signature levels (see the --edit-key command "tsign").
--check-sigs
Same as --list-sigs, but the signatures are verified.
--fingerprint
List all keys (or the specified ones) along with their finger
prints. This is the same output as --list-keys but with the
additional output of a line with the fingerprint. May also be
combined with --list-sigs or --check-sigs. If this command is
given twice, the fingerprints of all secondary keys are listed
too.
--list-packets
List only the sequence of packets. This is mainly useful for
debugging.
--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-cardHOWTO .
--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.
--delete-key name
Remove key from the public keyring. In batch mode either --yes
is required or the key must be specified by fingerprint. This is
a 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 fin
gerprint.
--export
Either export all keys from all keyrings (default keyrings and
those registered via option --keyring), or if at least one name
is given, those of the given name. The new keyring is written to
stdout or to the file given with option --output. Use together
with --armor to mail those keys.
--send-keys key IDs
Similar to --export but sends the keys to a keyserver. Finger
prints may be used instead of key IDs. Option --keyserver must
be used to give the name of this keyserver. Dont send your com
plete keyring to a keyserver --- select only those keys which
are new or changed by you.
--export-secret-keys
--export-secret-subkeys
Same as --export, but exports the secret keys instead. This is
normally not very useful and a security risk. The second form
of the command has the special property to render the secret
part of the primary key useless; this is a GNU extension to
OpenPGP and other implementations can not be expected to suc
cessfully import such a key. See the option --simple-sk-check
sum if you want to import such an exported key with an older
OpenPGP implementation.
--import
--fast-import
Import/merge keys. This adds the given keys to the keyring. The
fast version is currently just a synonym.
There are a few other options which control how this command
works. Most notable here is the --keyserver-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 keyserver.
--refresh-keys
Request updates from a keyserver for keys that already exist on
the local keyring. This is useful for updating a key with the
latest signatures, user IDs, etc. Calling this with no arguments
will refresh the entire keyring. Option --keyserver must be used
to give the name of the keyserver for all keys that do not have
preferred keyservers set (see --keyserver-options honor-key
server-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 meth
ods allow using the syntax specified in "How to specify a user
ID" below. Note that different keyserver types support different
search methods. Currently only LDAP supports them all.
--fetch-keys URIs
Retrieve keys located at the specified URIs. Note that different
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" values for keys.
The user has to give an estimation of how far she trusts the
owner of the displayed key to correctly certify (sign) other
keys. GnuPG only asks for the ownertrust value if it has not yet
been assigned to a key. Using the --edit-key menu, the assigned
value can be changed at any time.
--check-trustdb
Do trust database maintenance without user interaction. From
time to time the trust database must be updated so that expired
keys or signatures and the resulting changes in the Web of Trust
can be tracked. Normally, GnuPG will calculate when this is
required and do it automatically unless --no-auto-check-trustdb
is set. This command can be used to force a trust database check
at any time. The processing is identical to that of --update-
trustdb but it skips keys with a not yet defined "ownertrust".
For use with cron jobs, this command can be used together with
--batch in which case the trust database check is done only if a
check is needed. To force a run even in batch mode add the
option --yes.
--export-ownertrust
Send the ownertrust values to stdout. This is useful for backup
purposes as these values are the only ones which cant be re-
created from a corrupted trust DB.
--import-ownertrust
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
--print-mds
Print message digest of algorithm ALGO for all given files or
stdin. With the second form (or a deprecated "*" as algo)
digests for all available algorithms are printed.
--gen-random 0|1|2
Emit count random bytes of the given quality level. If count is
not given or zero, an endless sequence of random bytes will be
emitted. PLEASE, dont use this command unless you know what
you are doing; it may remove precious entropy from the system!
--gen-prime mode bits
Use the source, Luke :-). The output format is still subject to
change.
--enarmor
--dearmor
Pack or unpack an arbitrary input into/from an OpenPGP ASCII
armor. This is a GnuPG extension to OpenPGP and in general not
very useful.
How to manage your keys
This section explains the main commands for key management
--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 distri
bution on how to use this.
--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 elses key.
--edit-key
Present a menu which enables you to do most of the key manage
ment related tasks. It expects the specification of a key on
the command line.
sign Make a signature on key of user name If the key is not
yet signed by the default user (or the users given with
-u), the program displays the information of the key
again, together with its fingerprint and asks whether it
should be signed. This question is repeated for all users
specified with -u.
lsign Same as "sign" but the signature is marked as non-
exportable and will therefore never be used by others.
This may be used to make keys valid only in the local
environment.
nrsign Same as "sign" but the signature is marked as non-revoca
ble and can therefore never be revoked.
tsign Make a trust signature. This is a signature that combines
the notions of certification (like a regular signature),
and trust (like the "trust" command). It is generally
only useful in distinct communities or groups.
Note that "l" (for local / non-exportable), "nr" (for non-revo
cable, and "t" (for trust) may be freely mixed and prefixed to
"sign" to create a signature of any type desired.
revsig Revoke a signature. For every signature which has been
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 programs will scale it to fit
in a dialog box (PGP).
deluid Delete a user id. Note that it is not possible to
retract a user id, once it has been send to the public
(i.e. to a keyserver). In that case you better use
revuid.
delsig Delete a signature. Note that it is not possible to
retract a signature, once it has been send to the public
(i.e. to a keyserver). In that case you better use
revsig.
revuid Revoke a user id.
addkey Add a subkey to this key.
addcardkey
Generate a key on a card and add it to this key.
keytocard
Transfer the selected secret key (or the primary key if
no key has been selected) to a smartcard. The secret key
in the keyring will be replaced by a stub if the key
could be stored successfully on the card and you use the
save command later. Only certain key types may be trans
ferred to the card. A sub menu allows you to select on
what card to store the key. Note that it is not possible
to get that key back from the card - if the card gets
broken your secret key will be lost unless you have a
backup somewhere.
bkuptocard file
Restore the given file to a card. This command may be
used to restore a backup key (as generated during card
initialization) to a new card. In almost all cases this
will be the encryption key. You should use this command
only with the corresponding public key and make sure that
the file given as argument is indeed the backup to
restore. You should then select 2 to restore as encryp
tion 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 (secondart key). Note that it is not pos
sible to retract a subkey, once it has been send to the
public (i.e. to a keyserver). In that case you better
use revkey.
addrevoker
Add a designated revoker. This takes one optional argu
ment: "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 regu
lar user ID as primary makes it primary over other regu
lar user IDs.
uid n Toggle selection of user id with index n. Use 0 to dese
lect all.
key n Toggle selection of subkey with index n. Use 0 to dese
lect 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 pre
ferred keyserver and signature notations (if any) are
shown.
setpref string
Set the list of user ID preferences to string for all (or
just the selected) user IDs. Calling setpref with no
arguments sets the preference list to the default (either
built-in or set via --default-preference-list), and call
ing setpref with "none" as the argument sets an empty
preference list. Use gpg --version to get a list of
available algorithms. Note that while you can change the
preferences on an attribute user ID (aka "photo ID"),
GnuPG does not select keys via attribute user IDs so
these preferences will not be used by GnuPG.
keyserver
Set a preferred keyserver for the specified user ID(s).
This allows other users to know where you prefer they get
your key from. See --keyserver-options honor-keyserver-
url for more on how this works. Setting a value of
"none" removes an existing preferred keyserver.
notation
Set a name=value notation for the specified user ID(s).
See --cert-notation for more on how this works. Setting a
value of "none" removes all notations, setting a notation
prefixed with a minus sign (-) removes that notation, and
setting a notation name (without the =value) prefixed
with a minus sign removes all notations with that name.
toggle Toggle between public and secret key listing.
clean Compact (by removing all signatures except the selfsig)
any user ID that is no longer usable (e.g. revoked, or
expired). Then, remove any signatures that are not usable
by the trust calculations. Specifically, this removes
any signature that does not validate, any signature that
is superseded by a later signature, revoked signatures,
and signatures issued by keys that are not present on the
keyring.
minimize
Make the key as small as possible. This removes all sig
natures from each user ID except for the most recent
self-signature.
cross-certify
Add cross-certification signatures to signing subkeys
that may not currently have them. Cross-certification
signatures protect against a subtle attack against sign
ing 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 aster
isk. The trust value is displayed with the primary key: the
first is the assigned owner trust and the second is the calcu
lated 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 ver
sion 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-key.
OPTIONS
gpg comes features a bunch of options to control the exact behaviour
and to change the default configuration.
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.
Please remember that option parsing stops as soon as a non-option is
encountered, you can explicitly stop parsing by using the special
option --.
How to change the configuration
These options are used to change the configuraton and are usually found
in the option file.
--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.
--default-recipient name
Use name as default recipient if option --recipient is not used
and dont ask if this is a valid one. name must be non-empty.
--default-recipient-self
Use the default key as default recipient if option --recipient
is not used and dont 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.
-v, --verbose
Give more information during processing. If used twice, the
input data is listed in detail.
--no-verbose
Reset verbose level to 0.
-q, --quiet
Try to be as quiet as possible.
--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-
(after the two dashes) 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 list
ings. Defaults to no.
show-notations
show-std-notations
show-user-notations
Show all, IETF standard, or user-defined signature nota
tions in the --list-sigs or --check-sigs listings.
Defaults to no.
show-keyserver-urls
Show any preferred keyserver URL in the --list-sigs or
--check-sigs listings. Defaults to no.
show-uid-validity
Display the calculated validity of user IDs during key
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 listings to
show which keyring a given key resides on. Defaults to
no.
show-sig-expire
Show signature expiration dates (if any) during --list-
sigs or --check-sigs listings. Defaults to no.
show-sig-subpackets
Include signature subpackets in the key listing. This
option can take an optional argument list of the subpack
ets to list. If no argument is passed, list all subpack
ets. 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 nota
tions 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 veri
fication. 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 dis
close information on when and what signatures are veri
fied or to whom data is encrypted. This is similar to the
"web bug" described for the auto-key-retrieve feature.
pka-trust-increase
Raise the trust in a signature to full if the signature
passes PKA validation. This option is only meaningful if
pka-lookups is set.
--enable-dsa2
--disable-dsa2
Enables new-style DSA keys which (unlike the old style) may be
larger than 1024 bit and use hashes other than SHA-1 and
RIPEMD/160. Note that very few programs currently support these
keys and signatures from them.
--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 fingerprint, "%t" for the exten
sion 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 key
server helpers. If not provided, keyserver helpers use the com
piled-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.
--keyring file
Add file to the current list of keyrings. If file begins with a
tilde and a slash, these are replaced by the $HOME directory. If
the filename does not contain a slash, it is assumed to be in
the GnuPG home directory ("~/.gnupg" if --homedir or $GNUPGHOME
is not used).
Note that this adds a keyring to the current list. If the intent
is to use the specified keyring alone, use --keyring along with
--no-default-keyring.
--secret-keyring file
Same as --keyring but for the secret keyrings.
--primary-keyring file
Designate file as the primary public keyring. This means that
newly imported keys (via --import or keyserver --recv-from) will
go to this keyring.
--trustdb-name file
Use file instead of the default trustdb. If file begins with a
tilde and a slash, these are replaced by the $HOME directory. If
the filename does not contain a slash, it is assumed to be in
the GnuPG home directory (~/.gnupg if --homedir or $GNUPGHOME
is not used).
--homedir dir
Set the name of the home directory to dir. If this option is not
used, the home directory defaults to ~/.gnupg. It is only
recognized when given on the command line. It also overrides
any home directory stated through the environment variable
GNUPGHOME or (on W32 systems) by means of the Registry entry
HKCU\Software\GNU\GnuPG:HomeDir.
--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, win
scard.dll for Windows and libpcsclite.so for other systems.
--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 sup
port 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 termi
nal. A value of 0 refers to the first serial device; add 32768
to access USB devices. The default is 32768 (first USB device).
PC/SC or CCID readers might need a string here; run the program
in verbose mode to get a list of available readers. The default
is then the first reader found.
--display-charset name
Set the name of the native character set. This is used to con
vert some informational strings like user IDs to the proper
UTF-8 encoding. Note that this has nothing to do with the char
acter 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 current 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.
-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 compres
sion 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.
--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.
--ask-cert-level
--no-ask-cert-level
When making a key signature, prompt for a certification level.
If this option is not specified, the certification level used is
set via --default-cert-level. See --default-cert-level for
information on the specific levels and how they are used. --no-
ask-cert-level disables this option. This option defaults to no.
--default-cert-level n
The default to use for the check level when signing a key.
0 means you make no particular claim as to how carefully you
verified the key.
1 means you believe the key is owned by the person who claims to
own it but you could not, or did not verify the key at all. This
is useful for a "persona" verification, where you sign the key
of a pseudonymous user.
2 means you did casual verification of the key. For example,
this could mean that you verified that the key fingerprint and
checked the user ID on the key against a photo ID.
3 means you did extensive verification of the key. For example,
this could mean that you verified the key fingerprint with the
owner of the key in person, and that you checked, by means of a
hard to forge document with a photo ID (such as a passport) that
the name of the key owner matches the name in the user ID on the
key, and finally that you verified (by exchange of email) that
the email address on the key belongs to the key owner.
Note that the examples given above for levels 2 and 3 are just
that: examples. In the end, it is up to you to decide just what
"casual" and "extensive" mean to you.
This option defaults to 0 (no particular claim).
--min-cert-level
When building the trust database, treat any signatures with a
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 dont want to keep your secret keys
(or one of them) online but still want to be able to check the
validity of a given recipients or signators key.
--trust-model pgp|classic|direct|always|auto
Set what trust model GnuPG should follow. The models are:
pgp This is the Web of Trust combined with trust signatures
as used in PGP 5.x and later. This is the default trust
model when creating a new trust database.
classic
This is the standard Web of Trust as used in PGP 2.x and
earlier.
direct Key validity is set directly by the user and not calcu
lated via the Web of Trust.
always Skip key validation and assume that used keys are always
fully trusted. You generally wont use this unless you
are using some external validation scheme. This option
also suppresses the "[uncertain]" tag printed with signa
ture 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.
--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@exam
ple.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 --keyserver
option may be used here to query that particular key
server.
--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 conve
nient) 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
Use name as your keyserver. This is the server that --recv-keys,
--send-keys, and --search-keys will communicate with to receive
keys from, send keys to, and search for keys on. The format of
the name is a URI: scheme:[//]keyservername[:port] The scheme
is the type of keyserver: "hkp" for the HTTP (or compatible)
keyservers, "ldap" for the LDAP keyservers, or "mailto" for the
Graff email keyserver. Note that your particular installation of
GnuPG may have other keyserver types available as well. Key
server schemes are case-insensitive. After the keyserver name,
optional keyserver configuration options may be provided. These
are the same as the global --keyserver-options from below, but
apply only to this particular keyserver.
Most keyservers synchronize with each other, so there is gener
ally 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
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 export
ing (--send-key) a key from a keyserver. While not all options
are available for all keyserver types, some common options are:
include-revoked
When searching for a key with --search-keys, include keys
that are marked on the keyserver as revoked. Note that
not all keyservers differentiate between revoked and
unrevoked keys, and for such keyservers this option is
meaningless. Note also that most keyservers do not have
cryptographic verification of key revocations, and so
turning this option off may result in skipping keys that
are incorrectly marked as revoked.
include-disabled
When searching for a key with --search-keys, include keys
that are marked on the keyserver as disabled. Note that
this option is not used with HKP keyservers.
auto-key-retrieve
This option enables the automatic retrieving of keys from
a keyserver when verifying signatures made by keys that
are not on the local keyring.
Note that this option makes a "web bug" like behavior
possible. Keyserver operators can see which keys you
request, so by 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 preferred key
server to refresh the key from. In addition, if auto-key-
retrieve is set, and the signature being verified has a
preferred keyserver URL, then use that preferred key
server to fetch the key from. Defaults to yes.
honor-pka-record
If auto-key-retrieve is set, and the signature being ver
ified 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 tar
gets. Note that this option is not used with HKP key
servers, 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 tempo
rary 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 key
server communication protocol by reading the temporary
files.
verbose
Tell the keyserver helper program to be more verbose.
This option can be repeated multiple times to increase
the verbosity level.
timeout
Tell the keyserver helper program how long (in seconds)
to try and perform a keyserver action before giving up.
Note that performing multiple actions at the same time
uses this timeout value per action. For example, when
retrieving multiple keys via --recv-keys, the timeout
applies separately to each key retrieval, and not to the
--recv-keys command as a whole. Defaults to 30 seconds.
http-proxy
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 vari
able "http_proxy", if any, will be used.
max-cert-size
When retrieving a key via DNS CERT, only accept keys up
to this size. Defaults to 16384 bytes.
--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).
--simple-sk-checksum
Secret keys are integrity protected by using a SHA-1 checksum.
This method is part of the upcoming enhanced OpenPGP specifica
tion but GnuPG already uses it as a countermeasure against cer
tain attacks. Old applications dont understand this new for
mat, 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).
--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 modi
fications, you can use this option to disable the caching. It
probably does not make sense to disable it because all kind of
damage can be done if someone else has write access to your pub
lic 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 cre
ation 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.
--use-agent
--no-use-agent
Try to use the GnuPG-Agent. 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
been given
--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 corruption.
--exit-on-status-write-error
This option will cause write errors on the status FD to immedi
ately 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 wont break applications 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 operations.
--limit-card-insert-tries n
With n greater than 0 the number of prompts asking to insert a
smartcard gets limited to N-1. Thus with a value of 1 gpg wont
at all ask to insert a card if none has been inserted at
startup. This option is useful in the configuration file in case
an application does not know about the smartcard support and
waits ad infinitum for an inserted card.
--no-random-seed-file
GnuPG uses a file to store its internal random pool over invoca
tions. This makes random generation faster; however sometimes
write operations are not desired. This option can be used to
achieve that with the cost of slower random generation.
--no-greeting
Suppress the initial copyright message.
--no-secmem-warning
Suppress the warning about "using insecure memory".
--no-permission-warning
Suppress the warning about unsafe file and home directory
(--homedir) permissions. Note that the permission checks that
GnuPG performs are not intended to be authoritative, but rather
they simply warn about certain common permission problems. Do
not assume that the lack of a warning means that your system is
secure.
Note that the warning for unsafe --homedir permissions cannot be
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 warn
ing 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).
--require-cross-certification
--no-require-cross-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 sub
keys that can sign. Defaults to --require-cross-certification
for gpg.
--expert
--no-expert
Allow the user to do certain nonsensical or "silly" things like
signing an expired or revoked key, or certain potentially incom
patible things like generating unusual key types. This also dis
ables certain warning messages about potentially incompatible
actions. As the name implies, this option is for experts only.
If you dont fully understand the implications of what it allows
you to do, leave this off. --no-expert disables this option.
Key related options
--recipient name
-r Encrypt for user id name. If this option or --hidden-recipient
is not specified, GnuPG asks for the user-id unless --default-
recipient is given.
--hidden-recipient name
-R Encrypt for user ID name, but hide the key ID of this users
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.
--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 hid
den "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.
--group name=value1
Sets up a named group, which is similar to aliases in email pro
grams. Any time the group name is a recipient (-r or
--recipient), it will be expanded to the values specified. Mul
tiple groups with the same name are automatically merged into a
single group.
The values are key IDs or fingerprints, but any key description
is accepted. Note that a value with spaces in it will be treated
as two different values. Note also there is only one level of
expansion --- you cannot make an group that points to another
group. When used from the command line, it may be necessary to
quote the argument to this option to prevent the shell from
treating it as multiple arguments.
--ungroup name
Remove a given entry from the --group list.
--no-groups
Remove all entries from the --group list.
--local-user name
-u Use name as the key to sign with. Note that this option over
rides --default-key.
--try-all-secrets
Dont 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.
Input and Output
--armor
-a Create ASCII armored output. The default is to create the
binary OpenPGP format.
--no-armor
Assume the input data is not in ASCII armored format.
--output file
-o 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 plaintext of a
given message may be significantly larger than the original
OpenPGP message. While GnuPG works properly with such messages,
there is often a desire to set a maximum file size that will be
generated before processing is forced to stop by the OS limits.
Defaults to 0, which means "no limit".
--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 signa
tures 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 doesnt
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 run
ning 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 signa
tures 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 modified. Defaults to no.
--with-colons
Print key listings delimited by colons. Note that the output
will be encoded in UTF-8 regardless of any --display-charset
setting. This format is useful when GnuPG is called from scripts
and other programs as it is easily machine parsed. The details
of this format are documented in the file doc/DETAILS, which
is included in the GnuPG source distribution.
--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.
--with-fingerprint
Same as the command --fingerprint but changes only the format of
the output and may be used together with another command.
OpenPGP protocol specific options.
-t, --textmode
--no-textmode
Treat input files as text and store them in the OpenPGP canoni
cal text form with standard "CRLF" line endings. This also sets
the necessary flags to inform the recipient that the encrypted
or signed data is text and may need its line endings converted
back to whatever the local system uses. This option is useful
when communicating between two platforms that have different
line ending conventions (UNIX-like to Mac, Mac to Windows, etc).
--no-textmode disables this option, and is the default.
If -t (but not --textmode) is used together with armoring and
signing, this enables clearsigned messages. This kludge is
needed for command-line compatibility with command-line versions
of PGP; normally you would use --sign or --clearsign to select
the type of the signature.
--force-v3-sigs
--no-force-v3-sigs
OpenPGP states that an implementation should generate v4 signa
tures but PGP versions 5 through 7 only recognize v4 signatures
on key material. This option forces v3 signatures for signatures
on data. Note that this option overrides --ask-sig-expire, as
v3 signatures cannot have expiration dates. --no-force-v3-sigs
disables this option.
--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 block
size greater than 64 bits), or if all of the recipient keys
indicate MDC support in their feature flags.
--disable-mdc
Disable the use of the modification detection code. Note that by
using this option, the encrypted message becomes vulnerable to a
message modification attack.
--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 recipi
ent key preferences. The most highly ranked cipher in this list
is also used for the --symmetric encryption command.
--personal-digest-preferences string
Set the list of personal digest preferences to string, this list
should be a string similar to the one printed by the command
"pref" in the edit menu. This allows the user to factor in their
own preferred algorithms when algorithms are chosen via recipi
ent key preferences. The most highly ranked digest algorithm in
this list is algo used when signing without encryption (e.g.
--clearsign or --sign). The default value is SHA-1.
--personal-compress-preferences string
Set the list of personal compression preferences to string, this
list should be a string similar to the one printed by the com
mand "pref" in the edit menu. This allows the user to factor in
their own preferred algorithms when algorithms are chosen via
recipient key preferences. The most highly ranked algorithm in
this list is also used when there are no recipient keys to con
sider (e.g. --symmetric).
--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 con
ventional 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 number of times (see --s2k-count). Unless --rfc1991
is used, this mode is also used for conventional encryption.
--s2k-count n
Specify how many times the passphrase mangling is repeated.
This value may range between 1024 and 65011712 inclusive, and
the default is 65536. Note that not all values in the
1024-65011712 range are legal and if an illegal value is
selected, GnuPG will round up to the nearest legal value. This
option is only meaningful if --s2k-mode is 3.
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 behav
ior (see --openpgp), but with some additional workarounds for
common compatibility problems in different versions of PGP. This
is the default option, so it is not generally needed, but it may
be useful to override a different compliance option in the
gpg.conf file.
--openpgp
Reset all packet, cipher and digest options to strict OpenPGP
behavior. Use this option to reset all previous options like
--rfc1991, --force-v3-sigs, --s2k-*, --cipher-algo, --digest-
algo and --compress-algo to OpenPGP compliant values. All PGP
workarounds are disabled.
--rfc2440
Reset all packet, cipher and digest options to strict RFC-2440
behavior. Note that this is currently the same thing as
--openpgp.
--rfc1991
Try to be more RFC-1991 (PGP 2.x) compliant.
--pgp2 Set up all options to be as PGP 2.x compliant as possible, and
warn if an action is taken (e.g. encrypting to a non-RSA key)
that will create a message that PGP 2.x will not be able to han
dle. Note that PGP 2.x here means MIT PGP 2.6.2. There are
other versions of PGP 2.x available, but the MIT release is a
good common baseline.
This option implies --rfc1991 --disable-mdc --no-force-v4-certs
--no-sk-comment --escape-from-lines --force-v3-sigs --no-ask-
sig-expire --no-ask-cert-expire --cipher-algo IDEA --digest-algo
MD5 --compress-algo 1. It also disables --textmode when encrypt
ing.
--pgp6 Set up all options to be as PGP 6 compliant as possible. This
restricts you to the ciphers IDEA (if the IDEA plugin is
installed), 3DES, and CAST5, the hashes MD5, SHA1 and RIPEMD160,
and the compression algorithms none and ZIP. This also disables
--throw-keyids, and making signatures with signing subkeys as
PGP 6 does not understand signatures made by signing subkeys.
This option implies --disable-mdc --no-sk-comment --escape-from-
lines --force-v3-sigs --no-ask-sig-expire.
--pgp7 Set up all options to be as PGP 7 compliant as possible. This is
identical to --pgp6 except that MDCs are not disabled, and the
list of allowable ciphers is expanded to add AES128, AES192,
AES256, and TWOFISH.
--pgp8 Set up all options to be as PGP 8 compliant as possible. PGP 8
is a lot closer to the OpenPGP standard than previous versions
of PGP, so all this does is disable --throw-keyids and set
--escape-from-lines. All algorithms are allowed except for the
SHA224, SHA384, and SHA512 digests.
Doing things one usually dont want to do.
-n
--dry-run
Dont make any changes (this is not completely implemented).
--list-only
Changes the behaviour of some commands. This is like --dry-run
but different in some cases. The semantic of this command may be
extended in the future. Currently it only skips the actual
decryption pass and therefore enables a fast listing of the
encryption keys.
-i
--interactive
Prompt before overwriting any files.
--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 fron
tends to display a progress indicator while gpg is processing
larger files. There is a slight performance overhead using it.
--status-fd n
Write special status strings to the file descriptor n. See the
file DETAILS in the documentation for a listing of them.
--status-file file
Same as --status-fd, except the status data is written to file
file.
--logger-fd n
Write log output to file descriptor n and not to stderr.
--logger-file file
Same as --logger-fd, except the logger data is written to file
file.
--attribute-fd n
Write attribute subpackets to the file descriptor n. This is
most useful for use with --status-fd, since the status messages
are needed to 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 behav
ior 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 protected by the signature.
--emit-version
--no-emit-version
Force inclusion of the version string in ASCII armored output.
--no-emit-version disables this option.
--sig-notation name=value
--cert-notation name=value
-N, --set-notation name=value
Put the name value pair into the signature as notation data.
name must consist only of printable characters or spaces, and
must contain a @ character in the form keyname@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 overrides the @
check. value may be any printable string; it will be encoded in
UTF8, so you should check that your --display-charset is set
correctly. If you prefix name with an exclamation mark (!), the
notation data will be flagged as critical (rfc2440:5.2.3.15).
--sig-notation sets a notation for data signatures. --cert-nota
tion 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 fin
gerprint 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 mak
ing the signature (which might be a subkey), "%p" into the fin
gerprint 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.
--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 pol
icy url for data signatures. --cert-policy-url sets a policy url
for key signatures (certifications). --set-policy-url sets both.
The same %-expandos used for notation data are available here as
well.
--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 filename
of the file being encrypted.
--for-your-eyes-only
--no-for-your-eyes-only
Set the for your eyes only flag in the message. This causes
GnuPG to refuse to save the file unless the --output option is
given, and PGP to use the "secure viewer" with a Tempest-
resistant font to display the 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.
--cipher-algo name
Use name as cipher algorithm. Running the program with the com
mand --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. --per
sonal-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 compres
sion. "zip" is RFC-1951 ZIP compression which is used by PGP.
"bzip2" is a more modern compression scheme that can compress
some things better than zip or zlib, but at the cost of more
memory used during compression and decompression. "uncompressed"
or "none" disables compression. If this option is not used, the
default behavior is to examine the recipient key preferences to
see which algorithms the recipient supports. If all else fails,
ZIP is used for maximum compatibility.
ZLIB may give better compression results than ZIP, as the com
pression window size is not limited to 8k. BZIP2 may give even
better compression results than that, but will use a signifi
cantly larger amount of memory while compressing and decompress
ing. This may be significant in low memory situations. Note,
however, that PGP (all versions) only supports ZIP compression.
Using any algorithm other than ZIP or "none" will make the mes
sage unreadable with PGP. In general, you do not want to use
this option as it allows you to violate the OpenPGP standard.
--personal-compress-preferences is the safe way to accomplish
the same thing.
--cert-digest-algo name
Use name as the message digest algorithm used when signing a
key. Running the program with the command --version yields a
list of supported algorithms. Be aware that if you choose an
algorithm that GnuPG supports but other OpenPGP implementations
do not, then some users will not be able to use the key signa
tures you make, or quite possibly your entire key.
--disable-cipher-algo name
Never allow the use of name as cipher algorithm. The given name
will not be checked so that a later loaded algorithm will still
get disabled.
--disable-pubkey-algo name
Never allow the use of name as public key algorithm. The given
name will not be checked so that a later loaded algorithm will
still get disabled.
--throw-keyids
--no-throw-keyids
Do not put the recipient key IDs into encrypted messages. This
helps to hide the receivers of the message and is a limited
countermeasure against traffic analysis. On the receiving side,
it may slow down the decryption process because all available
secret keys must be tried. --no-throw-keyids disables this
option. This option is essentially the same as using --hidden-
recipient for all recipients.
--not-dash-escaped
This option changes the behavior of cleartext signatures so that
they can be used for patch files. You should not send such an
armored file via email because all spaces and line endings are
hashed too. You can not use this option for data which has 5
dashes at the beginning of a line, patch files dont 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 versions do it
this way too. Enabled by default. --no-escape-from-lines dis
ables this option.
--passphrase-repeat n
Specify how many times gpg will request a new passphrase be
repeated. This is useful for helping memorize a passphrase.
Defaults to 1 repetition.
--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.
Dont use this option if you can avoid it.
--passphrase string
Use string as the passphrase. This can only be used if only one
passphrase is supplied. Obviously, this is of very questionable
security on a multi-user system. Dont 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
--allow-non-selfsigned-uid
--no-allow-non-selfsigned-uid
Allow the import and use of keys with user IDs which are not
self-signed. This is not recommended, as a non self-signed user
ID is trivial to forge. --no-allow-non-selfsigned-uid disables.
--allow-freeform-uid
Disable all checks on the form of the user ID while generating a
new one. This option should only be used in very special envi
ronments 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, sometimes a sig
nature 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 checksum
against transmission errors. Occasionally the CRC gets mangled
somewhere on the transmission channel but the actual content
(which is protected by the OpenPGP protocol anyway) is still
okay. This option allows GnuPG to ignore CRC errors.
--ignore-mdc-error
This option changes a MDC integrity protection failure into a
warning. This can be useful if a message is partially corrupt,
but it is necessary to get as much data as possible out of the
corrupt message. However, be aware that a MDC protection fail
ure may also mean that the message was tampered with intention
ally by an attacker.
--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 pub
lic 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-key-data
Print key listings delimited by colons (like --with-colons) and
print the public key data.
--fast-list-mode
Changes the output of the list commands to work faster; this is
achieved by leaving some parts empty. Some applications dont
need the user ID and the trust information given in the list
ings. By using this options they can get a faster listing. The
exact behaviour of this option may change in future versions.
If you are missing some information, dont use this option.
--no-literal
This is not for normal use. Use the source to see for what it
might be useful.
--set-filesize
This is not for normal use. Use the source to see for what it
might be useful.
--show-session-key
Display the session key used for one message. See --override-
session-key for the counterpart of this option.
We think that Key Escrow is a Bad Thing; however the user should
have the freedom to decide whether to go to prison or to reveal
the content of one specific message without compromising all
messages ever encrypted for one secret key. DONT USE IT UNLESS
YOU ARE REALLY FORCED TO DO SO.
--override-session-key string
Dont 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 mes
sage; using this option you can do this without handing out the
secret key.
--ask-sig-expire
--no-ask-sig-expire
When making a data signature, prompt for an expiration time. If
this option is not specified, the expiration time set via
--default-sig-expire is used. --no-ask-sig-expire disables this
option. Note that by default, --force-v3-sigs is set which also
disables this option. If you want signature expiration, you must
set --no-force-v3-sigs as well as turning --ask-sig-expire on.
--default-sig-expire
The default expiration time to use for signature expiration.
Valid 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 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".
--allow-secret-key-import
This is an obsolete option and is not used anywhere.
--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.
--preserve-permissions
Dont 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.
--default-preference-list string
Set the list of default preferences to string. This preference
list is used for new keys and becomes the default for "setpref"
in the edit menu.
--default-keyserver-url name
Set the default keyserver URL to name. This keyserver will be
used as the keyserver URL when writing a new self-signature on a
key, which includes key generation and changing preferences.
--list-config
Display various internal configuration parameters of GnuPG. This
option is intended for external programs that call GnuPG to per
form 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.
--gpgconf-list
This command is simliar to --list-config but in general only
internally used by the gpgconf tool.
--gpgconf-test
This is more or less dummy action. However it parses the con
figuration file and returns with failure if the configuraion
file would prevent gpg from startup. Thus it may be used to run
a syntax check on the configuration file.
Deprecated options
--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/lib/gnupg"). Extensions are not generally use
ful anymore, and the use of this option is deprecated.
--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.
--show-keyring
Display the keyring name at the head of key listings to show
which keyring a given key resides on. This option is deprecated:
use --list-options [no-]show-keyring instead.
--ctapi-driver file
Use file to access the smartcard reader. The current default is
libtowitoko.so. Note that the use of this interface is depre
cated; it may be removed in future releases.
--always-trust
Identical to --trust-model always. This option is deprecated.
--show-notation
--no-show-notation
Show signature notations in the --list-sigs or --check-sigs
listings as well as when verifying a signature with a notation
in it. These options are deprecated. Use --list-options
[no-]show-notation and/or --verify-options [no-]show-notation
instead.
--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-pol
icy-url and/or --verify-options [no-]show-policy-url instead.
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
Verify the signature of the file but do not output the data. The
second form is used for detached signatures, where sigfile is
the detached signature (either ASCII armored or binary) and are
the signed data; if this is not given, the name of the file
holding the signed data is constructed by cutting off the exten
sion (".asc" or ".sig") of sigfile or by asking the user for the
filename.
HOW TO SPECIFY A USER ID
There are different ways to specify a user ID to GnuPG. Some of them
are only valid for gpg others are only good for gpgsm. Here is the
entire list of ways to specify a key:
By key Id.
This format is deduced from the length of the string and its
content or 0x prefix. The key Id of an X.509 certificate are the
low 64 bits of its SHA-1 fingerprint. The use of key Ids is
just a shortcut, for all automated processing the fingerprint
should be used.
When using gpg an exclamation mark may be appended to force
using the specified primary or secondary key and not to try and
calculate which primary or secondary key to use.
The last four lines of the example give the key ID in their long
form as internally used by the OpenPGP protocol. You can see the
long key ID using the option --with-colons.
234567C4
0F34E556E
01347A56A
0xAB123456
234AABBCC34567C4
0F323456784E56EAB
01AB3FED1347A5612
0x234AABBCC34567C4
By fingerprint.
This format is deduced from the length of the string and its
content or the 0x prefix. Note, that only the 20 byte version
fingerprint is available with gpgsm (i.e. the SHA-1 hash of the
certificate).
When using gpg an exclamation mark may be appended to force
using the specified primary or secondary key and not to try and
calculate which primary or secondary key to use.
The best way to specify a key Id is by using the fingerprint.
This avoids any ambiguities in case that there are duplicated
key IDs.
1234343434343434C434343434343434
123434343434343C3434343434343734349A3434
0E12343434343434343434EAB3484343434343434
0xE12343434343434343434EAB3484343434343434
(gpgsm also accepts colons between each pair of hexadecimal digits
because this is the de-facto standard on how to present X.509 finger
prints.)
By exact match on OpenPGP user ID.
This is denoted by a leading equal sign. It does not make sense
for X.509 certificates.
=Heinrich Heine
By exact match on an email address.
This is indicated by enclosing the email address in the usual
way with left and right angles.
By word match.
All words must match exactly (not case sensitive) but can appear
in any order in the user ID or a subjects name. Words are any
sequences of letters, digits, the underscore and all characters
with bit 7 set.
+Heinrich Heine duesseldorf
By exact match on the subjects DN.
This is indicated by a leading slash, directly followed by the
RFC-2253 encoded DN of the subject. Note that you cant use the
string printed by "gpgsm --list-keys" because that one as been
reordered and modified for better readability; use --with-colons
to print the raw (but standard escaped) RFC-2253 string
/CN=Heinrich Heine,O=Poets,L=Paris,C=FR
By exact match on the issuers DN.
This is indicated by a leading hash mark, directly followed by a
slash and then directly followed by the rfc2253 encoded DN of
the issuer. This should return the Root cert of the issuer.
See note above.
#/CN=Root Cert,O=Poets,L=Paris,C=FR
By exact match on serial number and issuers DN.
This is indicated by a hash mark, followed by the hexadecmal
representation of the serial number, the followed by a slash and
the RFC-2253 encoded DN of the issuer. See note above.
#4F03/CN=Root Cert,O=Poets,L=Paris,C=FR
By keygrip
This is indicated by an ampersand followed by the 40 hex digits
of a keygrip. gpgsm prints the keygrip when using the command
--dump-cert. It does not yet work for OpenPGP keys.
&D75F22C3F86E355877348498CDC92BD21010A480
By substring match.
This is the default mode but applications may want to explicitly
indicate this by putting the asterisk in front. Match is not
case sensitive.
Heine
*Heine
Please note that we have reused the hash mark identifier which was used
in old GnuPG versions to indicate the so called local-id. It is not
anymore used and there should be no conflict when used with X.509
stuff.
Using the RFC-2253 format of DNs has the drawback that it is not possi
ble to map them back to the original encoding, however we dont have to
do this because our key database stores this encoding as meta data.
RETURN VAUE
The program returns 0 if everything was fine, 1 if at least a signature
was bad, and other error codes for fatal errors.
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
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 compression
algorithms. It is important to be aware that not all OpenPGP programs
implement these optional algorithms and that by forcing their use via
the --cipher-algo, --digest-algo, --cert-digest-algo, or --compress-
algo options in GnuPG, it is possible to create a perfectly valid
OpenPGP message, but one that cannot be read by the intended recipient.
There are dozens of variations of OpenPGP programs available, and each
supports a slightly different subset of these optional algorithms. For
example, until recently, no (unhacked) version of PGP supported the
BLOWFISH cipher algorithm. A message using BLOWFISH simply could not be
read by a PGP user. By default, GnuPG uses the standard OpenPGP prefer
ences system that will always do the right thing and create messages
that are usable by all recipients, regardless of which OpenPGP program
they use. Only override this safe default if you really know what you
are doing.
If you absolutely must override the safe default, or if the preferences
on a given key are invalid for some reason, you are far better off
using the --pgp6, --pgp7, or --pgp8 options. These options are safe as
they do not force any particular algorithms in violation of OpenPGP,
but rather reduce the available algorithms to a "PGP-safe" list.
FILES
There are a few configuration files to control certain aspects of gpgs
operation. Unless noted, they are expected in the current home direc
tory (see: [option --homedir]).
gpg.conf
This is the standard configuration file read by gpg on startup.
It may contain any valid long option; the leading two dashes may
not be entered and the option may not be abbreviated. This
default name may be changed on the command line (see: [option
--options]).
Note that on larger installations, it is useful to put predefined files
into the directory /etc/skel/.gnupg/ so that newly created users
start up with a working configuration.
For internal purposes gpg creates and maintaines a few other files;
They all live in in the current home directory (see: [option --home
dir]). Only the gpg may modify these 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
/usr[/local]/share/gnupg/options.skel
Skeleton options file
/usr[/local]/lib/gnupg/
Default location for extensions
Operation is further controlled by a few environment variables:
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. This is 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 docu
mentation, 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.
BUGS
On many systems this program should be installed as setuid(root). This
is necessary to lock memory pages. Locking memory pages prevents the
operating system from writing memory pages (which may contain
passphrases or other sensitive material) to disk. If you get no warning
message about insecure memory your operating system supports locking
without being root. The program drops root privileges as soon as locked
memory is allocated.
SEE ALSO
gpgv(1),
The full documentation for this tool is maintained as a Texinfo manual.
If GnuPG and the info program are properly installed at your site, the
command
info gnupg1
should give you access to the complete manual including a menu struc
ture and an index.
GnuPG 1.4.6 2007-03-07 GPG(1)
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