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gpg(1) gpg(1)
NAME
gpg -- encryption and signing tool
SYNOPSIS
gpg [--homedir name] [--options file] [options] command [args]
DESCRIPTION
gpg is the main program for the GnuPG system.
This man page only lists the commands and options available. For more
verbose 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
Make a signature. This command may be combined with
--encrypt.
--clearsign
Make a clear text signature.
-b, --detach-sign
Make a detached signature.
-e, --encrypt
Encrypt data. This option may be combined with --sign.
-c, --symmetric
Encrypt with a symmetric cipher using a passphrase. The
default symmetric cipher used is CAST5, but may be chosen
with the --cipher-algo option.
--store Store only (make a simple RFC1991 packet).
--decrypt [file]
Decrypt file (or stdin if no file is specified) and write it
to stdout (or the file specified with --output). If the
decrypted file is signed, the signature is also verified.
This command differs from the default operation, as it never
writes to the filename which is included in the file and it
rejects files which don't begin with an encrypted message.
--verify [[sigfile] [signed-files]]
Assume that sigfile is a signature and verify it without
generating any output. With no arguments, the signa-
ture 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
signatures.
--verify-files [files]
Identical to '--multifile --verify'.
--encrypt-files [files]
Identical to '--multifile --encrypt'.
--decrypt-files [files]
Identical to '--multifile --decrypt'.
--list-keys [names]
--list-public-keys [names]
List all keys from the public keyrings, or just the ones
given on the command line.
Avoid using the output of this command in scripts or other
programs as it is likely to change as GnuPG changes. See
--with-colons for a machine-parseable key listing command
that is appropriate for use in scripts and other programs.
--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 addi-
tional 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 signa-
ture (see --nrsign-key), "P" for a signature that contains a
policy URL (see --cert-policy-url), "N" for a signature that
contains a notation (see --cert-notation), and "X" for an
eXpired signature (see --ask-cert-expire).
--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 fin-
gerprints 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
others. This may be used to make keys valid only
in the local environment.
nrsign Same as --sign but the signature is marked as non-
revocable and can therefore never be revoked.
nrlsign Combines the functionality of nrsign and lsign to
make a signature that is both non-revocable and
non-exportable.
revsig Revoke a signature. For every signature which has
been generated by one of the secret keys, GnuPG
asks whether a revocation certificate should be
generated.
trust Change the owner trust value. This updates the
trust-db immediately and no save is required.
disable
enable Disable or enable an entire key. A disabled key
can 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.
deluid Delete a user id.
delsig Delete a signature.
revuid Revoke a user id.
addkey Add a subkey to this key.
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 set-
ting a photo user ID as primary makes it primary
over other photo user IDs, and setting a regular
user ID as primary makes it primary over other
regular user IDs.
uid n Toggle selection of user id with index n. Use 0
to deselect all.
key n Toggle selection of subkey with index n. Use 0 to
deselect all.
check Check all selected user ids.
showphoto Display the selected photographic user id.
pref List preferences from the selected user ID. This
shows the actual preferences, without including
any implied preferences.
showpref More verbose preferences listing for the selected
user ID. This shows the preferences in effect by
including the implied preferences of 3DES
(cipher), SHA-1 (digest), and Uncompressed (com-
pression) if they are not already included in the
preference list.
setpref string
Set the list of user ID preferences to string,
this should be a string similar to the one printed
by "pref". Using an empty string will set the
default preference string, using "none" will set
the preferences to nil. Use "gpg -v --version" to
get a list of available algorithms. This command
just initializes an internal list and does not
change anything unless another command (such as
"updpref") which changes the self-signatures is
used.
updpref Change the preferences of all user IDs (or just of
the selected ones to the current list of prefer-
ences. The timestamp of all affected self-signa-
tures will be advanced by one second. Note that
while you can change the preferences on an
attribute user ID (aka "photo ID"), GnuPG does not
select keys via attribute user IDs so these pref-
erences will not be used by GnuPG.
toggle Toggle between public and secret key listing.
save Save all changes to the key rings and quit.
quit Quit the program without updating the key rings.
The listing shows you the key with its secondary keys and
all user ids. Selected keys or user ids are indicated by an
asterisk. The trust value is displayed with the primary key:
the first is the assigned owner trust and the second is the
calculated trust value. Letters are used for the values:
- No ownertrust assigned / not yet calculated.
e Trust calculation has failed; probably due to an
expired key.
q Not enough information for calculation.
n Never trust this key.
m Marginally trusted.
f Fully trusted.
u Ultimately trusted.
--sign-key name
Signs a public key with your secret key. This is a shortcut
version of the subcommand "sign" from --edit.
--lsign-key name
Signs a public key with your secret key but marks it as non-
exportable. This is a shortcut version of the subcommand
"lsign" from --edit.
--nrsign-key name
Signs a public key with your secret key but marks it as non-
revocable. This is a shortcut version of the subcommand
"nrsign" from --edit.
--delete-key name
Remove key from the public keyring. In batch mode either
--yes is required or the key must be specified by finger-
print. This is a safeguard against accidental deletion of
multiple keys.
--delete-secret-key name
Remove key from the secret and public keyring. In batch mode
the key must be specified by fingerprint.
--delete-secret-and-public-key name
Same as --delete-key, but if a secret key exists, it will be
removed first. In batch mode the key must be specified by
fingerprint.
--gen-revoke 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 --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 [key IDs]
Request updates from a keyserver for keys that already exist
on the local keyring. This is useful for updating a key
with the latest signatures, user IDs, etc. Calling this
with no arguments will refresh the entire keyring. Option
--keyserver must be used to give the name of this keyserver.
--search-keys [names]
Search the keyserver for the given names. Multiple names
given here will be joined together to create the search
string for the keyserver. Option --keyserver must be used
to give the name of this keyserver.
--update-trustdb
Do trust 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
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
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 over-
written.
--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 automati-
cally 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
plaintext of a given message may be significantly larger
than the original OpenPGP message. While GnuPG works prop-
erly 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
The Windows version of GnuPG replaces the extension of an
output filename to avoid problems with filenames containing
more than one dot. This is not necessary for newer Windows
versions and so --no-mangle-dos-filenames can be used to
switch this feature off and have GnuPG append the new exten-
sion. This option 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 is not specified,
GnuPG asks for the user-id unless --default-recipient is
given
--default-recipient name
Use name as default recipient if option --recipient is not
used and don't ask if this is a valid one. name must be non-
empty.
--default-recipient-self
Use the default key as default recipient if option --recipi-
ent is not used and don't ask if this is a valid one. The
default key is the first one from the secret keyring or the
one set with --default-key.
--no-default-recipient
Reset --default-recipient and --default-recipient-self.
--encrypt-to name
Same as --recipient but this one is intended for use in the
options file and may be used with your own user-id as an
"encrypt-to-self". These keys are only used when there are
other recipients given either by use of --recipient or by
the asked user id. No trust checking is performed for these
user ids and even disabled keys can be used.
--no-encrypt-to
Disable the use of all --encrypt-to keys.
-v, --verbose
Give more information during processing. If used twice, the
input data is listed in detail.
-q, --quiet
Try to be as quiet as possible.
-z n, --compress-level n
Set compression level to n. A value of 0 for n disables com-
pression. The default is to use the default compression
level of zlib (normally 6).
--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 very high compression 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
versions of PGP; normally you would use --sign or --clear-
sign 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
sometimes prints warnings to the TTY if --batch is used.
--yes Assume "yes" on most questions.
--no Assume "no" on most questions.
--ask-cert-level
--no-ask-cert-level
When making a key signature, prompt for a certification
level. If this option is not specified, the certification
level used is set via --default-cert-level. See --default-
cert-level for information on the specific levels and how
they are used. --no-ask-cert-level disables this option.
This option defaults to yes.
--min-cert-level
When building the trust database, disregard any signatures
with a certification level below this. Defaults to 1, which
accepts all signatures.
--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 exam-
ple, this could mean that you verified that the key finger-
print 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 finger-
print 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).
--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 sig-
nator's key.
--trust-model classic|always
Set what trust model GnuPG should follow. The models are:
classic This is the regular web-of-trust as used in PGP
and GnuPG.
always Skip key validation and assume that used keys are
always fully trusted. You won't use this unless
you have installed some external validation
scheme. This option also suppresses the "[uncer-
tain]" tag printed with signature checks when
there is no evidence that the user ID is bound to
the key.
--always-trust
Identical to '--trust-model always'. This option is depre-
cated.
--keyserver name
Use name as your keyserver. This is the server that --recv-
keys, --send-keys, and --search-keys will communicate with
to receive keys from, send keys to, and search for keys on.
The format of the name is a URI: 'scheme:[//]keyserver-
name[:port]' The scheme is the type of keyserver: "hkp" for
the HTTP (or compatible) keyservers, "ldap" for the NAI LDAP
keyserver, or "mailto" for the Graff email keyserver. Note
that your particular installation of GnuPG may have other
keyserver types available as well. Keyserver schemes are
case-insensitive.
Most keyservers synchronize with each other, so there is
generally no need to send keys to more than one server. The
keyserver "hkp://subkeys.pgp.net" uses round robin DNS to
give a different keyserver each time you use it.
--keyserver-options parameters
This is a space or comma delimited string that gives options
for the keyserver. Options can be prepended with a 'no-' to
give the opposite meaning. Valid import-options or export-
options may be used here as well to apply to importing
(--recv-key) or exporting (--send-key) a key from a key-
server. While not all options are available for all key-
server types, some common options are:
include-revoked
When searching for a key 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 crypto-
graphic verification of key revocations, and so
turning this option off may result in skipping
keys that are incorrectly marked as revoked.
Defaults to on.
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.
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
reading the temporary files.
verbose Tell the keyserver helper program to be more ver-
bose. This option can be repeated multiple times
to increase the verbosity level.
honor-http-proxy
For keyserver schemes that use HTTP (such as HKP),
try to access the keyserver over the proxy set
with the environment variable "http_proxy".
auto-key-retrieve
This option enables the automatic retrieving of
keys from a keyserver when verifying signatures
made by keys that are not on the local keyring.
Note that this option makes a "web bug" like
behavior possible. Keyserver operators can see
which keys you request, so by sending you a mes-
sage signed by a brand new key (which you natu-
rally will not have on your local keyring), the
operator can tell both your IP address and the
time when you verified the signature.
--import-options parameters
This is a space or comma delimited string that gives options
for importing keys. Options can be prepended with a 'no-'
to give the opposite meaning. The options are:
allow-local-sigs
Allow importing key signatures marked as "local".
This is not generally useful unless a shared
keyring scheme is being used. Defaults to no.
repair-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.
--export-options parameters
This is a space or comma delimited string that gives options
for exporting keys. Options can be prepended with a 'no-'
to give the opposite meaning. The options are:
include-non-rfc
Include non-RFC compliant keys in the export.
Defaults to yes.
include-local-sigs
Allow exporting key signatures marked as "local".
This is not generally useful unless a shared
keyring scheme is being used. Defaults to no.
include-attributes
Include attribute user IDs (photo IDs) while
exporting. This is useful to export keys if they
are going to be used by an OpenPGP program that
does not accept attribute user IDs. Defaults to
yes.
include-sensitive-revkeys
Include designated revoker information that was
marked as "sensitive". Defaults to no.
--show-photos
--no-show-photos
Causes --list-keys, --list-sigs, --list-public-keys, --list-
secret-keys, and verifying a signature to also display the
photo ID attached to the key, if any. See also --photo-
viewer. --no-show-photos disables this option.
--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 nei-
ther %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.
--show-keyring
Causes --list-keys, --list-public-keys, and --list-secret-
keys to display the name of the keyring a given key resides
on. This is only useful when you're listing a specific key
or set of keys. It has no effect when listing all keys.
--keyring file
Add file to the 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.
--trustdb-name file
Use file instead of the default trustdb. If file begins
with a tilde and a slash, these are replaced by the $HOME
directory. If the filename does not contain a slash, it is
assumed to be in the GnuPG home directory ("~/.gnupg" if
--homedir or $GNUPGHOME is not used).
--homedir directory
Set the name of the home directory to directory If this
option is not used it defaults to "~/.gnupg". It does not
make sense to use this in a options file. This also over-
rides the environment variable $GNUPGHOME.
--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. 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 argu-
ments. Both options may be used multiple times.
--options file
Read options from file and do not try to read them from the
default options file in the homedir (see --homedir). This
option is ignored if used in an options file.
--no-options
Shortcut for "--options /dev/null". This option is detected
before an attempt to open an option file. Using this option
will also prevent the creation of a "~./gnupg" homedir.
--load-extension name
Load an extension module. If name does not contain a slash
it is searched for in the directory configured when GnuPG
was built (generally "/usr/local/lib/gnupg"). Extensions
are not generally useful anymore, and the use of this option
is deprecated.
--debug flags
Set debugging flags. All flags are or-ed and flags may be
given in C syntax (e.g. 0x0042).
--debug-all
Set all useful debugging flags.
--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 over-
head 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.
--logger-fd n
Write log output to file descriptor n and not to stderr.
--attribute-fd n
Write attribute subpackets to the file descriptor n. This
is most useful for use with --status-fd, since the status
messages are needed to separate out the various subpackets
from the stream delivered to the file descriptor.
--sk-comments
--no-sk-comments
Include secret key comment packets when exporting secret
keys. This is a GnuPG extension to the OpenPGP standard,
and is off by default. Please note that this has nothing to
do with the comments in clear text signatures or armor head-
ers. --no-sk-comments disables this option.
--no-comment
See --no-sk-comments. This option is deprecated and may be
removed soon.
--comment string
Use string as the comment string in ASCII armored or clear-
signed messages. The default behavior is to not use a com-
ment string.
--default-comment
Force to write the standard comment string in clear text
signatures. Use this to overwrite a --comment from a config
file. This option is now obsolete because there is no
default comment string anymore.
--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. This is to help prevent
pollution of the IETF reserved notation namespace. The
--expert flag overrides the 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-nota-
tion 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, and "%%" results in a single
"%". %k, %K, and %f are only meaningful when making a key
signature (certification).
--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. --no-show-notation disables this option.
--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 (cer-
tifications). --set-policy-url sets both.
The same %-expandos used for notation data are available
here as well.
--show-policy-url
--no-show-policy-url
Show policy URLs in the --list-sigs or --check-sigs listings
as well as when verifying a signature with a policy URL in
it. --no-show-policy-url disables this option.
--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.
--digest-algo name
Use name as the message digest algorithm. Running the pro-
gram with the command --version yields a list of supported
algorithms.
--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 implemen-
tations do not, then some users will not be able to use the
key signatures you make, or quite possibly your entire key.
--s2k-cipher-algo name
Use name as the cipher algorithm used to protect secret
keys. The default cipher is CAST5. This cipher is also
used for conventional encryption if --cipher-algo is not
given.
--s2k-digest-algo name
Use name as the digest algorithm used to mangle the
passphrases. The default algorithm is SHA-1. This digest
algorithm is also used for conventional encryption if
--digest-algo is not given.
--s2k-mode n
Selects how passphrases are mangled. If n is 0 a plain
passphrase (which is not recommended) will be used, a 1 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).
--compress-algo n
Use compression algorithm n. The value 2 is RFC1950 ZLIB
compression. The value 1 is RFC-1951 ZIP compression which
is used by PGP. 0 disables compression. If this option is
not used, the default behavior is to examine the recipient
key preferences to see which algorithms the recipient sup-
ports. If all else fails, ZIP is used for maximum compati-
bility. Note, however, that ZLIB may give better compres-
sion results if that is more important, as the compression
window size is not limited to 8k.
--disable-cipher-algo name
Never allow the use of name as cipher algorithm. The given
name will not be checked so that a later loaded algorithm
will still get disabled.
--disable-pubkey-algo name
Never allow the use of name as public key algorithm. The
given name will not be checked so that a later loaded
algorithm will still get disabled.
--no-sig-cache
Do not cache the verification status of key signatures.
Caching gives a much better performance in key listings.
However, if you suspect that your public keyring is not save
against write modifications, you can use this option to dis-
able the caching. It probably does not make sense to dis-
able 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 verifi-
cation 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
Do not put the recipient keyid into encrypted packets. This
option hides the receiver of the message and is a counter-
measure against traffic analysis. It may slow down the
decryption process because all available secret keys are
tried.
--not-dash-escaped
This option changes the behavior of cleartext signatures so
that they can be used for patch files. You should not send
such an armored file via email because all spaces and line
endings are hashed too. You can not use this option for
data which has 5 dashes at the beginning of a line, patch
files don't have this. A special armor header line tells
GnuPG about this cleartext signature option.
--escape-from-lines
--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 sys-
tem from breaking the signature. Note that all other PGP
versions do it this way too. Enabled by default. --no-
escape-from-lines disables this option.
--passphrase-fd n
Read the passphrase from file descriptor n. If you use 0 for
n, the passphrase will be read from stdin. This can only be
used if only one passphrase is supplied. Don't use this
option if you can avoid it.
--command-fd n
This is a replacement for the deprecated shared-memory IPC
mode. If this option is enabled, user input on questions is
not expected from the TTY but from the given file descrip-
tor. It should be used together with --status-fd. See the
file doc/DETAILS in the source distribution for details on
how to use it.
--use-agent
--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 com-
pliance 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
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 SHA384 and SHA512 digests.
--force-v3-sigs
--no-force-v3-sigs
OpenPGP states that an implementation should generate v4
signatures but PGP versions 5 through 7 only recognize v4
signatures on key material. This option forces v3 signa-
tures for signatures on data. Note that this option over-
rides --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
vulnerable 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 stan-
dard 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 warn-
ing. 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 signa-
tures.
--ignore-crc-error
The ASCII armor used by OpenPGP is protected by a CRC check-
sum against transmission errors. Sometimes it happens that
the CRC gets mangled somewhere on the transmission channel
but the actual content (which is protected by the OpenPGP
protocol anyway) is still okay. This option will let gpg
ignore CRC errors.
--ignore-mdc-error
This option changes a MDC integrity protection failure into
a warning. This can be useful if a message is partially
corrupt, but it is necessary to get as much data as possible
out of the corrupt message. However, be aware that a MDC
protection failure may also mean that the message was tam-
pered 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 corruption.
--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 gen-
eration.
--no-verbose
Reset verbose level to 0.
--no-greeting
Suppress the initial copyright message.
--no-secmem-warning
Suppress the warning about "using insecure memory".
--no-permission-warning
Suppress the warning about unsafe file and home directory
(--homedir) permissions. Note that the permission checks
that GnuPG performs are not intended to be authoritative,
but rather they simply warn about certain common permission
problems. Do not assume that the lack of a warning means
that your system is secure.
Note that the warning for unsafe --homedir permissions can-
not be supressed in the gpg.conf file, as this would allow
an attacker to place an unsafe gpg.conf file in place, and
use this file to supress warnings about itself. The --home-
dir permissions warning may only be supressed on the command
line.
--no-mdc-warning
Suppress the warning about missing MDC integrity protection.
--no-armor
Assume the input data is not in ASCII armored format.
--no-default-keyring
Do not add the default keyrings to the list of keyrings.
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 out-
put 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 dis-
tribution.
--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 for-
mat of the output and may be used together with another com-
mand.
--fast-list-mode
Changes the output of the list commands to work faster; this
is achieved by leaving some parts empty. Some applications
don't need the user ID and the trust information given in
the listings. By using this options they can get a faster
listing. The exact behaviour of this option may change in
future versions.
--fixed-list-mode
Do not merge primary user ID and primary key in --with-colon
listing mode and print all timestamps as seconds since
1970-01-01.
--list-only
Changes the behaviour of some commands. This is like --dry-
run but 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
listing of the encryption keys.
--no-literal
This is not for normal use. Use the source to see for what
it might be useful.
--set-filesize
This is not for normal use. Use the source to see for what
it might be useful.
--emulate-md-encode-bug
GnuPG versions prior to 1.0.2 had a bug in the way a signa-
ture was encoded. This options enables a workaround by
checking faulty signatures again with the encoding used in
old versions. This may only happen for Elgamal signatures
which are not widely used.
--show-session-key
Display the session key used for one message. See --over-
ride-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 com-
promising all messages ever encrypted for one secret key.
DON'T USE IT UNLESS YOU ARE REALLY FORCED TO DO SO.
--override-session-key string
Don't use the public key but the session key string. The
format of this string is the same as the one printed by
--show-session-key. This option is normally not used but
comes handy in case someone forces you to reveal the content
of an encrypted message; using this option you can do this
without handing out the secret key.
--ask-sig-expire
--no-ask-sig-expire
When making a data signature, prompt for an expiration time.
If this option is not specified, the expiration time is
"never". --no-ask-sig-expire disables this option.
--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 is
"never". --no-ask-cert-expire disables this option.
--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 deprecated key
types. This also disables certain warning messages about
potentially incompatible actions. As the name implies, this
option is for experts only. If you don't fully understand
the implications of what it allows you to do, leave this
off. --no-expert disables this option.
--merge-only
Don't insert new keys into the keyrings while doing an
import.
--allow-secret-key-import
This is an obsolete option and is not used anywhere.
--try-all-secrets
Don't look at the key ID as stored in the message but try
all secret keys in turn to find the right decryption key.
This option forces the behaviour as used by anonymous recip-
ients (created by using --throw-keyids) and might come handy
in case where an encrypted message contains a bogus key ID.
--enable-special-filenames
This options enables a mode in which filenames of the form
-&n, where n is a non-negative decimal number, refer to the
file descriptor n and not to a file with that name.
--no-expensive-trust-checks
Experimental use only.
--group name=value1 [value2 value3 ...]
Sets up a named group, which is similar to aliases in email
programs. Any time the group name is a 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.
--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 default value is
"H2" indicating 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.
--default-preference-list string
Set the list of default preferences to string, this list
should be a string similar to the one printed by the command
"pref" in the edit menu. This affects both key generation
and "updpref" in the edit menu.
--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
Using an exact to match string. The equal sign indicates
this.
Using the email address part which must match exactly. The
left angle bracket indicates this email address mode.
+Heinrich Heine duesseldorf
All words must match exactly (not case sensitive) but can
appear in any order in the user ID. Words are any sequences
of letters, digits, the underscore and all characters with
bit 7 set.
Heine
*Heine By case insensitive substring matching. This is the default
mode but applications may want to explicitly indicate this
by putting the asterisk in front.
Note that you can append an exclamation mark (!) to key IDs or finger-
prints. This flag tells GnuPG to use 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 signa-
ture 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.
http_proxy
Only honored when the keyserver-option honor-http-proxy is
set.
FILES
~/.gnupg/secring.gpg
The secret keyring
~/.gnupg/secring.gpg.lock
and the lock file
~/.gnupg/pubring.gpg
The public keyring
~/.gnupg/pubring.gpg.lock
and the lock file
~/.gnupg/trustdb.gpg
The trust database
~/.gnupg/trustdb.gpg.lock
and the lock file
~/.gnupg/random_seed
used to preserve the internal random pool
~/.gnupg/gpg.conf
Default configuration file
~/.gnupg/options
Old style configuration file; only used when gpg.conf is not
found
/usr[/local]/share/gnupg/options.skel
Skeleton options file
/usr[/local]/lib/gnupg/
Default location for extensions
WARNINGS
Use a *good* password for your user account and a *good* passphrase to
protect your secret key. This passphrase is the weakest part of the
whole system. Programs to do dictionary attacks on your secret
keyring are very easy to write and so you should protect your
"~/.gnupg/" directory very well.
Keep in mind that, if this program is used over a network (telnet), it
is *very* easy to spy out your passphrase!
If you are going to verify detached signatures, make sure that the
program knows about it; either give both filenames on the command line
or use - to specify stdin.
INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS
GnuPG tries to be a very flexible implementation of the OpenPGP 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 com-
pression algorithms. It is important to be aware that not all OpenPGP
programs implement these optional algorithms and that by forcing their
use via the --cipher-algo, --digest-algo, --cert-digest-algo, or
--compress-algo options in GnuPG, it is possible to create a perfectly
valid OpenPGP message, but one that cannot be read by the intended
recipient.
There are dozens of variations of OpenPGP programs available, and each
supports a slightly different subset of these optional algorithms.
For example, until recently, no (unhacked) version of PGP supported
the BLOWFISH cipher algorithm. A message using BLOWFISH simply could
not be read by a PGP user. By default, GnuPG uses the standard
OpenPGP preferences system that will always do the right thing and
create messages that are usable by all recipients, regardless of which
OpenPGP program they use. Only override this safe default if you
really know what you are doing.
If you absolutely must override the safe default, or if the prefer-
ences 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)
UNIX/Linux commands referenced on this page: