gpg(1) - phpMan

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 man-
agement and all bells and whistles you can expect from a decent OpenPGP implementation.

This is the standalone version of gpg. For desktop use you should consider using gpg2.

RETURN VALUE
The program returns 0 if everything was fine, 1 if at least a signature was bad, and other
error codes for fatal errors.

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
GnuPG tries to be a very flexible implementation of the OpenPGP standard. 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 preferences
system that will always do the right thing and create messages that are usable by all
recipients, regardless of which OpenPGP program they use. Only override this safe default
if you really know what you are doing.

If you absolutely must override the safe default, or if the preferences on a given key are
invalid for some reason, you are far better off using the --pgp6, --pgp7, or --pgp8
options. These options are safe as they do not force any particular algorithms in viola-
tion of OpenPGP, but rather reduce the available algorithms to a "PGP-safe" list.

COMMANDS
Commands are not distinguished from options except for the fact that only one command is
allowed.

gpg may be run with no commands, in which case it will perform a reasonable action depend-
ing on the type of file it is given as input (an encrypted message is decrypted, a signa-
ture is verified, a file containing 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 abbrevi-
ate 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 abbrevi-
ate 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 --symmetric 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 signature is readable
without any special software. OpenPGP software is only needed to verify the signa-
ture. Clear text signatures may modify end-of-line whitespace for platform indepen-
dence 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 message 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 oper-
ation, 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
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 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
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 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

-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 nonRevoca-
ble signature (see the --edit-key command "nrsign"), "P" for a signature that con-
tains a policy URL (see --cert-policy-url), "N" for a signature that contains a
notation (see --cert-notation), "X" for an eXpired signature (see --ask-cert-
expire), and the numbers 1-9 or "T" for 10 and above to indicate trust signature
levels (see the --edit-key command "tsign").

--check-sigs
Same as --list-sigs, but the signatures are verified.

The status of the verification is indicated by a flag directly following the "sig"
tag (and thus before the flags described above for --list-sigs). A "!" indicates
that the signature has been successfully verified, a "-" denotes a bad signature
and a "%" is used if an error occured while checking the signature (e.g. a non sup-
ported algorithm).

--fingerprint
List all keys (or the specified ones) along with their fingerprints. This is the
same output as --list-keys but with the additional output of a line with the fin-
gerprint. 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 dele-
tion of multiple keys.

--delete-secret-key name
Remove key from the secret and public keyring. In batch mode the key must be speci-
fied 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.

--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. Fingerprints may be used
instead of key IDs. Option --keyserver must be used to give the name of this key-
server. Don't send your complete 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 prop-
erty 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 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

--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. Call-
ing 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-keyserver-url).

--search-keys names
Search the keyserver for the given names. Multiple names given here will be joined
together to create the search string for the keyserver. Option --keyserver must be
used to give the name of this keyserver. Keyservers that support different search
methods allow using the syntax specified in "How to specify a user ID" below. Note
that different keyserver types support different search methods. Currently only
LDAP supports them all.

--fetch-keys URIs
Retrieve keys located at the specified URIs. Note that different 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 process-
ing 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
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 sec-
ond 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, don't use this com-
mand 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 distribution 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 else's key.

--edit-key
Present a menu which enables you to do most of the key management 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 informa-
tion 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 there-
fore 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 there-
fore 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" com-
mand). It is generally only useful in distinct communities or groups.

Note that "l" (for local / non-exportable), "nr" (for non-revocable, and "t" (for
trust) may be freely mixed and 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 gen-
erated.

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 bet-
ter 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 transferred to the card. A
sub menu allows you to select on what card to store the key. Note that it is
not possible to get that key back from the card - if the card gets broken
your secret key will be lost unless you have a backup somewhere.

bkuptocard file
Restore the given file to a card. This command may be used to restore a
backup key (as generated during card initialization) to a new card. In
almost all cases this will be the encryption key. You should use this com-
mand only with the corresponding public key and make sure that the file
given as argument is indeed the backup to restore. You should then select 2
to restore as encryption key. You will first be asked to enter the
passphrase of the backup key and then for the Admin PIN of the card.

delkey Remove a subkey (secondart key). Note that it is not possible 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 argument: "sensitive". If
a designated revoker is marked as sensitive, it will not be exported by
default (see export-options).

revkey Revoke a subkey.

expire Change the key expiration time. If a subkey is selected, the expiration time
of this subkey will be changed. With no selection, the key expiration of the
primary key is changed.

passwd Change the passphrase of the secret key.

primary
Flag the current user id as the primary one, removes the primary user id
flag from all other user ids and sets the timestamp of all affected self-
signatures one second ahead. Note that setting a photo user ID as primary
makes it primary over other photo user IDs, and setting a regular user ID as
primary makes it primary over other 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 prefer-
ences, without including any implied preferences.

showpref
More verbose preferences listing for the selected user ID. This shows the
preferences in effect by including the implied preferences of 3DES (cipher),
SHA-1 (digest), and Uncompressed (compression) if they are not already
included in the preference list. In addition, the preferred keyserver and
signature notations (if any) are shown.

setpref string
Set the list of user ID preferences to string for all (or just the selected)
user IDs. Calling setpref with no arguments sets the preference list to the
default (either built-in or set via --default-preference-list), and calling
setpref with "none" as the argument sets an empty preference list. Use gpg
--version to get a list of available algorithms. Note that while you can
change the preferences on an attribute user ID (aka "photo ID"), GnuPG does
not select keys via attribute user IDs so these preferences will not be used
by GnuPG.

keyserver
Set a preferred keyserver for the specified user ID(s). This allows other
users to know where you prefer they get your key from. See --keyserver-
options honor-keyserver-url for more on how this works. Setting a value of
"none" removes an existing preferred keyserver.

notation
Set a name=value notation for the specified user ID(s). See --cert-notation
for more on how this works. Setting a value of "none" removes all notations,
setting a notation prefixed with a minus sign (-) removes that notation, and
setting a notation name (without the =value) prefixed with a minus sign
removes all notations with that name.

toggle Toggle between public and secret key listing.

clean Compact (by removing all signatures except the selfsig) any user ID that is
no longer usable (e.g. revoked, or expired). Then, remove any signatures
that are not usable by the trust calculations. Specifically, this removes
any signature that does not validate, any signature that is superseded by a
later signature, revoked signatures, and signatures issued by keys that are
not present on the keyring.

minimize
Make the key as small as possible. This removes all signatures from each
user ID except for the most recent self-signature.

cross-certify
Add cross-certification signatures to signing subkeys that may not currently
have them. Cross-certification signatures protect against a subtle attack
against signing subkeys. See --require-cross-certification.

save Save all changes to the key rings and quit.

quit Quit the program without updating the key rings.

The listing shows you the key with its secondary keys and all user ids. Selected
keys or user ids are indicated by an asterisk. The trust value is displayed with
the primary key: the first is the assigned owner trust and the second is the 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 version of the subcom-
mand "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 configuration 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 don't ask if
this is a valid one. name must be non-empty.

--default-recipient-self
Use the default key as default recipient if option --recipient is not used and
don't ask if this is a valid one. The default key is the first one from the secret
keyring or the one set with --default-key.

--no-default-recipient
Reset --default-recipient and --default-recipient-self.

-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.

--batch

--no-batch
Use batch mode. Never ask, do not allow interactive commands. --no-batch disables
this option.

--no-tty
Make sure that the TTY (terminal) is never used for any output. This option is
needed in some cases because GnuPG sometimes prints warnings to the TTY even if
--batch is used.

--yes Assume "yes" on most questions.

--no Assume "no" on most questions.

--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 listings. Defaults to
no.

show-notations

show-std-notations

show-user-notations
Show all, IETF standard, or user-defined signature notations in the --list-
sigs or --check-sigs listings. Defaults to no.

show-keyserver-urls

Show any preferred keyserver URL in the --list-sigs or --check-sigs list-
ings. 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 subpackets to list. If no argument is passed,
list all subpackets. Defaults to no. This option is only meaningful when
using --with-colons along with --list-sigs or --check-sigs.

--verify-options parameters
This is a space or comma delimited string that gives options used when verifying
signatures. Options can be prepended with a `no-' to give the opposite meaning. The
options are:

show-photos
Display any photo IDs present on the key that issued the signature.
Defaults to no. See also --photo-viewer.

show-policy-urls
Show policy URLs in the signature being verified. Defaults to no.

show-notations

show-std-notations

show-user-notations
Show all, IETF standard, or user-defined signature notations in the signa-
ture being verified. Defaults to IETF standard.

show-keyserver-urls
Show any preferred keyserver URL in the signature being verified. Defaults
to no.

show-uid-validity
Display the calculated validity of the user IDs on the key that issued the
signature. Defaults to no.

show-unusable-uids
Show revoked and expired user IDs during signature verification. Defaults
to no.

show-primary-uid-only
Show only the primary user ID during signature verification. That is all
the AKA lines as well as photo Ids are not shown with the signature verifi-
cation status.

pka-lookups
Enable PKA lookups to verify sender addresses. Note that PKA is based on
DNS, and so enabling this option may disclose information on when and what
signatures are verified or to whom data is encrypted. This is similar to the
"web bug" described for the auto-key-retrieve feature.

pka-trust-increase
Raise the trust in a signature to full if the signature passes PKA valida-
tion. 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 cur-
rently 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 extension of
the image type (e.g. "jpg"), "%T" for the MIME type of the image (e.g.
"image/jpeg"), and "%%" for an actual percent sign. If neither %i or %I are
present, then the photo will be supplied to the viewer on standard input.

The default viewer is "xloadimage -fork -quiet -title 'KeyID 0x%k' stdin". Note
that if your image viewer program is not secure, then executing it from GnuPG does
not make it secure.

--exec-path string
Sets a list of directories to search for photo viewers and keyserver helpers. If
not provided, keyserver helpers use the compiled-in default directory, and photo
viewers use the $PATH environment variable. Note, that on W32 system this value is
ignored when searching for keyserver helpers.

--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\\Soft-
ware\\GNU\\GnuPG:HomeDir.

--pcsc-driver file
Use file to access the smartcard reader. The current default is `libpcsclite.so.1'
for GLIBC based systems, `/System/Library/Frameworks/PCSC.framework/PCSC' for MAC
OS X, `winscard.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 support is only available if libusb was available at build time.

--reader-port number_or_string
This option may be used to specify the port of the card terminal. A value of 0
refers to the first serial device; add 32768 to access USB devices. The default is
32768 (first USB device). PC/SC or CCID readers might need a string here; run the
program in verbose mode to get a list of available readers. The default is then the
first reader found.

--display-charset name
Set the name of the native character set. This is used to convert some informa-
tional strings like user IDs to the proper UTF-8 encoding. Note that this has
nothing to do with the character set of data to be encrypted or signed; GnuPG does
not recode user-supplied data. If this option is not used, the default character
set is determined from the 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 spec-
ified 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 compression level for the BZIP2 compression algorithm (defaulting to
6 as well). This is a different option from --compress-level since BZIP2 uses a
significant amount of memory for each additional compression level. -z sets both.
A value of 0 for n disables compression.

--bzip2-decompress-lowmem
Use a different decompression method for BZIP2 compressed files. This alternate
method uses a bit more than half the memory, but also runs at half the speed. This
is useful under extreme low memory circumstances when the file was originally com-
pressed 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 out-
put 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" verifi-
cation, 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 pass-
port) that the name of the key owner matches the name in the user ID on the key,
and finally that you verified (by exchange of email) that the email address on the
key belongs to the key owner.

Note that the examples given above for levels 2 and 3 are just that: examples. In
the end, it is up to you to decide just what "casual" and "extensive" mean to you.

This option defaults to 0 (no particular claim).

--min-cert-level
When building the trust database, treat any signatures with a certification level
below this as invalid. Defaults to 2, which disregards level 1 signatures. Note
that level 0 "no particular claim" signatures are always accepted.

--trusted-key long key ID
Assume that the specified key (which must be given as a full 8 byte key ID) is as
trustworthy as one of your own secret keys. This option is useful if you don't want
to keep your secret keys (or one of them) online but still want to be able to check
the validity of a given recipient's or signator's key.

--trust-model pgp|classic|direct|always|auto
Set what trust model GnuPG should follow. The models are:

pgp This is the Web of Trust combined with trust 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 calculated via the Web of
Trust.

always Skip key validation and assume that used keys are always fully trusted. You
generally won't use this unless you are using some external validation
scheme. This option also suppresses the "[uncertain]" tag printed with sig-
nature 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 AT example.com" form), and
there are no user AT example.com keys on the local keyring. This option takes any num-
ber of the following arguments, in the order they are to be tried:

cert locate a key using DNS CERT, as specified in 2538bis (currently in draft):
http://www.josefsson.org/rfc2538bis/

pka locate a key using DNS PKA.

ldap locate a key using the PGP Universal method of checking "ldap://keys.(thedo-
main)".

keyserver
locate a key using whatever keyserver is defined using the --keyserver
option.

(keyserver URL)
In addition, a keyserver URL as used in the --keyserver option may be used
here to query that particular keyserver.

--keyid-format short|0xshort|long|0xlong
Select how to display key IDs. "short" is the traditional 8-character key ID.
"long" is the more accurate (but less convenient) 16-character key ID. Add an "0x"
to either to include an "0x" at the beginning of the key ID, as in 0x99242560.

--keyserver name
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. Keyserver schemes are case-insensitive. After the keyserver name, optional
keyserver configuration options may be provided. These are the same as the global
--keyserver-options from below, but apply only to this particular keyserver.

Most keyservers synchronize with each other, so there is generally no need to send
keys to more than one server. The keyserver hkp://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 exporting (--send-key) a key from a keyserver. While not all options are
available for all keyserver types, some common options are:

include-revoked
When searching for a key with --search-keys, include keys that are marked on
the keyserver as revoked. Note that not all keyservers differentiate between
revoked and unrevoked keys, and for such keyservers this option is meaning-
less. 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 key-
servers.

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 keyserver to refresh the key from. In addition,
if auto-key-retrieve is set, and the signature being verified has a pre-
ferred keyserver URL, then use that preferred keyserver to fetch the key
from. Defaults to yes.

honor-pka-record
If auto-key-retrieve is set, and the signature being verified has a PKA
record, then use the PKA information to fetch the key. Defaults to yes.

include-subkeys
When receiving a key, include subkeys as potential targets. Note that this
option is not used with HKP keyservers, as they do not support retrieving
keys by subkey id.

use-temp-files
On most Unix-like platforms, GnuPG communicates with the keyserver helper
program via pipes, which is the most efficient method. This option forces
GnuPG to use temporary files to communicate. On some platforms (such as
Win32 and RISC OS), this option is always enabled.

keep-temp-files
If using `use-temp-files', do not delete the temp files after using them.
This option is useful to learn the keyserver communication protocol by read-
ing the temporary files.

verbose
Tell the keyserver helper program to be more 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=value
Set the proxy to use for HTTP and HKP keyservers. This overrides the
"http_proxy" environment variable, if any.

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 specification but GnuPG already uses it as a coun-
termeasure 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).

--no-sig-cache
Do not cache the verification status of key signatures. Caching gives a much bet-
ter performance in key listings. However, if you suspect that your public keyring
is not save against write modifications, you can use this option to disable the
caching. It probably does not make sense to disable it because all kind of damage
can be done if someone else has write access to your public keyring.

--no-sig-create-check
GnuPG normally verifies each signature right after creation to protect against bugs
and hardware malfunctions which could leak out bits from the secret key. This extra
verification needs some time (about 115% for DSA keys), and so this option can be
used to disable it. However, due to the fact that the signature creation needs
manual interaction, this 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 con-
suming 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 'GPG_AGENT_INFO''. This is only used
when --use-agent has been given. Given that this option is not anymore used by
gpg2, it should be avoided if possible.

--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 environ-
ments, where it can be assured that only one process is accessing those files. A
bootable floppy with a stand-alone encryption system will probably use this.
Improper usage of this option may lead to data and key corruption.

--exit-on-status-write-error
This option will cause write errors on the status FD to immediately terminate the
process. That should in fact be the default but it never worked this way and thus
we need an option to enable this, so that the change won't break 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 opera-
tions.

--limit-card-insert-tries n
With n greater than 0 the number of prompts asking to insert a smartcard gets lim-
ited to N-1. Thus with a value of 1 gpg won't at all ask to insert a card if none
has been inserted at startup. This option is useful in the configuration file in
case an application does not know about the smartcard support and waits ad infini-
tum for an inserted card.

--no-random-seed-file
GnuPG uses a file to store its internal random pool over invocations. This makes
random generation faster; however sometimes write operations are not desired. This
option can be used to achieve that with the cost of slower random generation.

--no-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 authori-
tative, 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 permis-
sions warning may only be suppressed on the command line.

--no-mdc-warning
Suppress the warning about missing MDC integrity protection.

--require-secmem

--no-require-secmem
Refuse to run if GnuPG cannot get secure memory. Defaults to no (i.e. run, but give
a warning).

--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 sub-
tle attack against subkeys that can sign. Defaults to --require-cross-certifica-
tion 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 incompatible things like generating unusual
key types. This also disables certain warning messages about potentially incompati-
ble 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.

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 user's key. This option helps
to hide the receiver of the message and is a limited countermeasure against traffic
analysis. If this option or --recipient is not specified, GnuPG asks for the user
ID unless --default-recipient is given.

--encrypt-to name
Same as --recipient but this one is intended for use in the options file and may be
used with your own user-id as an "encrypt-to-self". These keys are only used when
there are other recipients given either by use of --recipient or by the asked user
id. No trust checking is performed for these user ids and even disabled keys can
be used.

--hidden-encrypt-to name
Same as --hidden-recipient but this one is intended for use in the options file and
may be used with your own user-id as a hidden "encrypt-to-self". These keys are
only used when there are other recipients given either by use of --recipient or by
the asked user id. No trust checking is performed for these user ids and even dis-
abled 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 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 sin-
gle 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 argu-
ments.

--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 overrides --default-key.

--try-all-secrets
Don't look at the key ID as stored in the message but try all secret keys in turn
to find the right decryption key. This option forces the behaviour as used by
anonymous recipients (created by using --throw-keyids) and might come handy in case
where an encrypted message contains a bogus key ID.

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 pro-
cessing a file. Since OpenPGP supports various levels of compression, it is possi-
ble 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 use-
ful unless a shared keyring scheme is being used. Defaults to no.

repair-pks-subkey-bug
During import, attempt to repair the damage caused by the PKS keyserver bug
(pre version 0.9.6) that mangles keys with multiple subkeys. Note that this
cannot completely repair the damaged key as some crucial data is removed by
the keyserver, but it does at least give you back one subkey. Defaults to no
for regular --import and to yes for keyserver --recv-keys.

merge-only
During import, allow key updates to existing keys, but do not allow any new
keys to be imported. Defaults to no.

import-clean
After import, compact (remove all signatures except the self-signature) any
user IDs from the new key that are not usable. Then, remove any signatures
from the new key that are not usable. This includes signatures that were
issued by keys that are not present on the keyring. This option is the same
as running the --edit-key command "clean" after import. Defaults to no.

import-minimal
Import the smallest key possible. This removes all signatures except the
most recent self-signature on each user ID. This option is the same as run-
ning 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 use-
ful unless a shared keyring scheme is being used. Defaults to no.

export-attributes
Include attribute user IDs (photo IDs) while exporting. This is useful to
export keys if they are going to be used by an OpenPGP program that does not
accept attribute user IDs. Defaults to yes.

export-sensitive-revkeys
Include designated revoker information that was marked as "sensitive".
Defaults to no.

export-reset-subkey-passwd
When using the --export-secret-subkeys command, this option resets the
passphrases for all exported subkeys to empty. This is useful when the
exported subkey is to be used on an unattended machine where a passphrase
doesn't necessarily make sense. Defaults to no.

export-clean
Compact (remove all signatures from) user IDs on the key being exported if
the user IDs are not usable. Also, do not export any signatures that are not
usable. This includes signatures that were issued by keys that are not
present on the keyring. This option is the same as running the --edit-key
command "clean" before export except that the local copy of the key is not
modified. Defaults to no.

export-minimal
Export the smallest key possible. This removes all signatures except the
most recent self-signature on each user ID. This option is the same as run-
ning 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 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 commu-
nicating 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 signatures but PGP ver-
sions 5 through 7 only recognize v4 signatures on key material. This option forces
v3 signatures for signatures on data. Note that this option implies --ask-sig-
expire, --sig-policy-url, --sig-notation, and --sig-keyserver-url, as these fea-
tures cannot be used with v3 signatures. --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.

--personal-cipher-preferences string
Set the list of personal cipher preferences to string. Use gpg --version to get a
list of available algorithms, and use none to set no preference at all. This
allows the user to factor in their own preferred algorithms when algorithms are
chosen via recipient key preferences. The most highly ranked cipher in this list
is also used for the --symmetric encryption command.

--personal-digest-preferences string
Set the list of personal digest preferences to string. Use gpg --version to get a
list of available algorithms, and use none to set no preference at all. This
allows the user to factor in their own preferred algorithms when algorithms are
chosen via recipient key preferences. The most highly ranked digest algorithm in
this list is algo used when signing without encryption (e.g. --clearsign or
--sign). The default value is SHA-1.

--personal-compress-preferences string
Set the list of personal compression preferences to string. Use gpg --version to
get a list of available algorithms, and use none to set no preference at all. This
allows the user to factor in their own preferred algorithms when algorithms are
chosen via recipient key preferences. The most highly ranked compression algorithm
in this list is algo used when there are no recipient keys to consider (e.g. --sym-
metric).

--s2k-cipher-algo name
Use name as the cipher algorithm used to protect secret keys. The default cipher
is CAST5. This cipher is also used for conventional encryption if --personal-
cipher-preferences and --cipher-algo is not given.

--s2k-digest-algo name
Use name as the digest algorithm used to mangle the passphrases. The default algo-
rithm 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 behavior (see --openpgp),
but with some additional workarounds for common compatibility problems in different
versions of PGP. This is the default option, so it is not generally needed, but it
may be useful to override a different compliance option in the gpg.conf file.

--openpgp
Reset all packet, cipher and digest options to strict OpenPGP behavior. Use this
option to reset all previous options like --s2k-*, --cipher-algo, --digest-algo and
--compress-algo to OpenPGP compliant values. All PGP workarounds are disabled.

--rfc4880
Reset all packet, cipher and digest options to strict RFC-4880 behavior. Note that
this is currently the same thing as --openpgp.

--rfc2440
Reset all packet, cipher and digest options to strict RFC-2440 behavior.

--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 base-
line.

This option implies --rfc1991 --disable-mdc --no-force-v4-certs --no-sk-comment
--escape-from-lines --force-v3-sigs --cipher-algo IDEA --digest-algo MD5 --com-
press-algo ZIP. 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 under-
stand signatures made by signing subkeys.

This option implies --disable-mdc --no-sk-comment --escape-from-lines --force-
v3-sigs.

--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 doesn't want to do.

-n

--dry-run
Don't 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 smartcards. Note that this
option is only available on some system.

--enable-progress-filter
Enable certain PROGRESS status outputs. This option allows frontends to display a
progress indicator while gpg is processing larger files. There is a slight perfor-
mance 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 behavior is not to use a comment string. --com-
ment 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 signa-
ture.

--emit-version

--no-emit-version
Force inclusion of the version string in ASCII armored output. --no-emit-version
disables this option.

--sig-notation name=value

--cert-notation name=value

-N, --set-notation name=value
Put the name value pair into the signature as notation data. name must consist
only of printable characters or spaces, and must contain a '@' character in the
form keyname AT domain.com (substituting the 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-notation sets a notation for key signatures (certifica-
tions). --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 sig-
nature, "%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 signa-
ture, "%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 (cer-
tification), 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 policy 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 command --version yields
a list of supported algorithms. If this is not used the cipher algorithm is
selected from the preferences stored with the key. In general, you do not want to
use this option as it allows you to violate the OpenPGP standard. --personal-
cipher-preferences is the safe way to accomplish the same thing.

--digest-algo name
Use name as the message digest algorithm. Running the program with the command
--version yields a list of supported algorithms. In general, you do not want to use
this option as it allows you to violate the OpenPGP standard. --personal-digest-
preferences is the safe way to accomplish the same thing.

--compress-algo name
Use compression algorithm name. "zlib" is RFC-1950 ZLIB compression. "zip" is
RFC-1951 ZIP compression which is used by PGP. "bzip2" is a more modern compres-
sion 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 exam-
ine the recipient key preferences to see which algorithms the recipient supports.
If all else fails, ZIP is used for maximum compatibility.

ZLIB may give better compression results than ZIP, as the compression window size
is not limited to 8k. BZIP2 may give even better compression results than that, but
will use a significantly larger amount of memory while compressing and 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 message unreadable with PGP. In general, you do not want to
use this option as it allows you to violate the OpenPGP standard. --personal-com-
press-preferences is the safe way to accomplish the same thing.

--cert-digest-algo name
Use name as the message digest algorithm used when signing a key. Running the pro-
gram with the command --version yields a list of supported algorithms. Be aware
that if you choose an algorithm that GnuPG supports but other OpenPGP implementa-
tions do not, then some users will not be able to use the key signatures you make,
or quite possibly your entire key.

--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 avail-
able secret keys must be tried. --no-throw-keyids disables this option. This
option is essentially the same as using --hidden-recipient for all recipients.

--not-dash-escaped
This option changes the behavior of cleartext signatures so that they can be used
for patch files. You should not send such an armored file via email because all
spaces and line endings are hashed too. You can not use this option for data which
has 5 dashes at the beginning of a line, patch files don't have this. A special
armor header line tells GnuPG about this cleartext signature option.

--escape-from-lines

--no-escape-from-lines
Because some mailers change lines starting with "From " to ">From " it is good to
handle such lines in a special way when creating cleartext 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 disables this option.

--passphrase-repeat n
Specify how many times gpg will request a new passphrase be repeated. This is use-
ful 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. Don't use this option if you can avoid it.

--passphrase string
Use string as the passphrase. This can only be used if only one passphrase is sup-
plied. Obviously, this is of very questionable security on a multi-user system.
Don't use this option if you can avoid it.

--command-fd n
This is a replacement for the deprecated shared-memory IPC mode. If this option is
enabled, user input on questions is not expected from the TTY but from the given
file descriptor. It should be used together with --status-fd. See the file
doc/DETAILS in the source distribution for details on how to use it.

--command-file file
Same as --command-fd, except the commands are read out of file file

--allow-non-selfsigned-uid

--no-allow-non-selfsigned-uid
Allow the import and use of keys with user IDs which are not self-signed. This is
not recommended, as a non self-signed user ID is trivial to forge. --no-allow-non-
selfsigned-uid disables.

--allow-freeform-uid
Disable all checks on the form of the user ID while generating a new one. This
option should only be used in very special environments as it does not ensure the
de-facto standard format of user IDs.

--ignore-time-conflict
GnuPG normally checks that the timestamps associated with keys and signatures have
plausible values. However, sometimes a signature seems to be older than the key due
to clock problems. This option makes these checks just a warning. See also
--ignore-valid-from for timestamp issues on subkeys.

--ignore-valid-from
GnuPG normally does not select and use subkeys created in the future. This option
allows the use of such keys and thus exhibits the pre-1.0.7 behaviour. You should
not use this option unless you there is some clock problem. See also --ignore-time-
conflict for timestamp issues with 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
failure may also mean that the message was tampered with intentionally 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 alter-
nate 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-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 don't need the user ID and the trust informa-
tion 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. If you are miss-
ing some information, don't 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. 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 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-multiple-messages

--no-allow-multiple-messages
Allow processing of multiple OpenPGP messages contained in a single file or stream.
Some programs that call GPG are not prepared to deal with multiple messages being
processed together, so this option defaults to no. Note that versions of GPG prior
to 1.4.7 always allowed multiple messages.

--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
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.

--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 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.

--gpgconf-list
This command is similar 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 configuration file and
returns with failure if the configuration 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"). Exten-
sions are not generally useful 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 veri-
fying 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 deprecated; 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 veri-
fying a signature with a policy URL in it. These options are deprecated. Use
--list-options [no-]show-policy-url and/or --verify-options [no-]show-policy-url
instead.

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 extension (".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 pre-
fix. 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 fingerprints.)

By exact match on OpenPGP user ID.
This is denoted by a leading equal sign. It does not make sense for X.509 certifi-
cates.

=Heinrich Heine <heinrichh AT uni-duesseldorf.de>

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 subject's DN.
This is indicated by a leading slash, directly followed by the RFC-2253 encoded DN
of the subject. Note that you can't 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 issuer's 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 issuer's DN.
This is indicated by a hash mark, followed by the hexadecimal representation of the
serial number, then 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 ver-
sions 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 possible to map them back
to the original encoding, however we don't have to do this because our key database stores
this encoding as meta data.

FILES
There are a few configuration files to control certain aspects of gpg's operation. Unless
noted, they are expected in the current home directory (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 maintains a few other files; They all live in in the
current home directory (see: [option --homedir]). 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 documentation,
this variable is set to the correct value. The option --gpg-agent-info can be used
to override it.

PINENTRY_USER_DATA
This value is passed via gpg-agent to pinentry. It is useful to convey extra
information to a custom pinentry

COLUMNS

LINES Used to size some displays to the full size of the screen.

LANGUAGE
Apart from its use by GNU, it is used in the W32 version to override the language
selection done through the Registry. If used and set to a a valid and available
language name (langid), the file with the translation is loaded from
gpgdir/gnupg.nls/langid.mo. Here gpgdir is the directory out of which the gpg
binary has been laoded. If it can't be loaded the Registry is tried as a fallback.

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.

Note also that some systems (especially laptops) have the ability to ``suspend to disk''
(also known as ``safe sleep'' or ``hibernate''). This writes all memory to disk before
going into a low power or even powered off mode. Unless measures are taken in the operat-
ing system to protect the saved memory, passphrases or other sensitive material may be
recoverable from it later.