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 avail­ able. For a more verbose documentation get the GNU Pri­ vacy Handbook (GPH), which is available at http://www.gnupg.org/gph/ . You will find a list of HOWTO documents at http://www.gnupg.org/docs.html . Please remember that option parsing stops as soon as a non option is encountered, you can explicitly stop option parsing by using the special option "--". COMMANDS gpg recognizes these commands: -s, --sign Make a signature. This command may be combined with --encrypt. --clearsign Make a clear text signature. -b, --detach-sign Make a detached signature. -e, --encrypt Encrypt data. This option may be combined with --sign. -c, --symmetric Encrypt with symmetric cipher only. This com­ mand asks for a passphrase. --store Store only (make a simple RFC1991 packet). --decrypt [file] Decrypt file (or stdin if no file is specified) and write it to stdout (or the file specified with --output). If the decrypted file is signed, the signature is also verified. This command differs from the default operation, as it never writes to the filename which is included in the file and it rejects files which don't begin with an encrypted message. 1 gpg(1) gpg(1) --verify [[sigfile] [signed-files]] Assume that sigfile is a signature and verify it without generating any output. With no argu­ ments, 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 sig­ nature 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. --verify-files [files] This is a special version of the --verify com­ mand which does not work with detached signa­ tures. The command expects the files to be ver­ ified either on the command line or reads the filenames from stdin; each name must be on sep­ arate line. The command is intended for quick checking of many files. --list-keys [names] --list-public-keys [names] List all keys from the public keyrings, or just the ones given on the command line. --list-secret-keys [names] List all keys from the secret keyrings, or just the ones given on the command line. --list-sigs [names] Same as --list-keys, but the signatures are listed too. --check-sigs [names] Same as --list-sigs, but the signatures are ver­ ified. --fingerprint [names] List all keys with their fingerprints. This is the same output as --list-keys but with the additional output of a line with the finger­ print. 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 2 gpg(1) gpg(1) mainly useful for debugging. --gen-key Generate a new key pair. This command is nor­ mally 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 fingerprint and asks whether it should be signed. This question is repeated for all users specified with -u. lsign Same as --sign but the signature is marked as non-exportable and will therefore never be used by others. This may be used to make keys valid only in the local environment. nrsign Same as --sign but the signature is marked as non-revocable and can there­ fore 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. GnuPG asks for every signature which has been done by one of the secret keys, 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 normally not be used for encryption. 3 gpg(1) gpg(1) adduid Create an alternate user id. addphoto Create a photographic user id. deluid Delete a user id. addkey Add a subkey to this key. delkey Remove a subkey. revkey Revoke a subkey. expire Change the key expiration time. If a key is selected, the time of this key 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 pri­ mary 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 pri­ mary 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. showpref More verbose preferences listing. setpref string Set the list of user ID preferences to string, this should be a string simi­ lar to the one printed by "pref". Using an empty string will set the default preference string, using "none" will set the preferences to 4 gpg(1) gpg(1) nil. Only available algorithms are allowed. This command just initial­ izes an internal list and does not change anything unless another command 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 preferences. The timestamp of all affected self-signa­ tures fill be advanced by one second. 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 cal­ culated trust value. Letters are used for the values: - No ownertrust assigned / not yet cal­ culated. e Trust calculation has failed; probably due to an expired key. q Not enough information for calcula­ tion. 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 5 gpg(1) gpg(1) 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 --delete-secret-key name Remove key from the secret and public keyring --delete-secret-and-public-key name Same as --delete-key, but if a secret key exists, it will be removed first. --gen-revoke Generate a revocation certificate for the com­ plete key. To revoke a subkey or a signature, use the --edit command. --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 "output". Use together with --armor to mail those keys. --send-keys [names] Same as --export but sends the keys to a key­ server. Option --keyserver must be used to give the name of this keyserver. Don't send your com­ plete keyring to a keyserver - select only those keys which are new or changed by you. --export-all [names] Same as --export, but also exports keys which are not compatible with OpenPGP. --export-secret-keys [names] --export-secret-subkeys [names] Same as --export, but exports the secret keys instead. This is normally not very useful and a security risk. The second form of the command has the special property to render the secret part of the primary key useless; this is a GNU extension to OpenPGP and other implementations can not be expected to successfully import such a key. 6 gpg(1) gpg(1) 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 signa­ tures, 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. --search-keys [names] Search the keyserver for the given names. Mul­ tiple names given here will be joined together to create the search string for the keyserver. Option --keyserver must be used to give the name of this keyserver. --update-trustdb Do trust DB maintenance. This command goes over all keys and builds the Web-of-Trust. This is an interactive command because it may has to ask for the "ownertrust" values of keys. The user has to give an estimation in how far she trusts the owner of the displayed key to correctly cer­ tify (sign) other keys. It does only ask for that value if it has not yet been assigned to a key. Using the edit menu, that value can be changed at any time later. --check-trustdb Do trust DB maintenance without user interac­ tion. Form time to time the trust database must be updated so that expired keys and resulting changes in the Web-of-Trust can be tracked. GnuPG tries to figure when this is required and then does it implicitly; this command can be used to force such a check. The processing is identically to that of --update-trustdb but it skips keys with a not yet defined "ownertrust". For use with cron jobs, this command can be used together with --batch in which case the check is 7 gpg(1) gpg(1) only done when it is due. To force a run even in batch mode add the option --yes. --export-ownertrust [file] Store the ownertrust values into file (or stdin if not given). This is useful for backup pur­ poses 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); exist­ ing values will be overwritten. --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 avail­ able algorithms are printed. --gen-random 0|1|2 [count] Emit COUNT random bytes of the given quality level. If count is not given or zero, an endless sequence of random bytes will be emitted. PLEASE, don't use this command unless you know what you are doing; it may remove precious entropy from the system! --gen-prime mode bits [qbits] Use the source, Luke :-). The output format is still subject to change. --version Print version information along with a list of supported algorithms. --warranty Print warranty information. -h, --help Print usage information. This is a really long list even though it doesn't list all options. OPTIONS Long options can be put in an options file (default "~/.gnupg/options"). Do not write the 2 dashes, but sim­ ply the name of the option and any required arguments. Lines with a hash as the first non-white-space character are ignored. Commands may be put in this file too, but that does not make sense. gpg recognizes these options: 8 gpg(1) gpg(1) -a, --armor Create ASCII armored output. -o, --output file Write output to file. -u, --local-user name Use name as the user ID to sign. This option is silently ignored for the list commands, so that it can be used in an options file. --default-key name Use name as default user ID for signatures. If this is not used the default user ID is the first user ID found in the secret keyring. -r, --recipient name Encrypt for user id name. If this option is not specified, GnuPG asks for the user-id unless --default-recipient is given --default-recipient name Use name as default recipient if option --recip­ ient 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-recipi­ ent-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 recipi­ ents given either by use of --recipient or by the asked user id. No trust checking is per­ formed 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. 9 gpg(1) gpg(1) -q, --quiet Try to be as quiet as possible. -z n Set compression level to n. A value of 0 for n disables compression. Default is to use the default compression level of zlib (normally 6). -t, --textmode Use canonical text mode. If -t (but not --textmode) is used together with armoring and signing, this enables clearsigned messages. This kludge is needed for PGP compatibility; normally you would use --sign or --clearsign to selected the type of the signature. -n, --dry-run Don't make any changes (this is not completely implemented). -i, --interactive Prompt before overwriting any files. --batch Use batch mode. Never ask, do not allow inter­ active commands. --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 if --batch is used. --no-batch Disable batch mode. This may be of use if --batch is enabled from an options file. --yes Assume "yes" on most questions. --no Assume "no" on most questions. --default-cert-check-level n The default to use for the check level when signing a key. 0 means you make no particular claim as to how carefully you verified the key. 1 means you believe the key is owned by the per­ son who claims to own it but you could not, or did not verify the key at all. This is useful for a "persona" verification, where you sign the key of a pseudonymous user. 2 means you did casual verification of the key. For example, this could mean that you verified that the key fingerprint and checked the user ID 10 gpg(1) gpg(1) on the key against a photo ID. 3 means you did extensive verification of the key. For example, this could mean that you ver­ ified the key fingerprint with the owner of the key in person, and that you checked, by means of a hard to forge document with a photo ID (such as a passport) that the name of the key owner matches the name in the user ID on the key, and finally that you verified (by exchange of email) that the email address on the key belongs to the key owner. Note that the examples given above for levels 2 and 3 are just that: examples. In the end, it is up to you to decide just what "casual" and "extensive" mean to you. This option defaults to 0. --trusted-key long key ID Assume that the specified key (which must be given as a full 8 byte key ID) is as trustwor­ thy 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 recipi­ ent's or signator's key. --always-trust Skip key validation and assume that used keys are always fully trusted. You won't use this unless you have installed some external valida­ tion scheme. This option also suppresses the "[uncertain]" tag printed with signature checks when there is no evidence that the user ID is bound to the key. --keyserver name Use name as your keyserver. This is the server that --recv-keys, --send-keys, and --search-keys will communicate with to receive keys from, send keys to, and search for keys on. The format of the name is a URI: `scheme:[//]keyserver­ name[:port]' The scheme is the type of key­ server: "hkp" for the Horowitz (or compatible) keyservers, "ldap" for the NAI LDAP keyserver, or "mailto" for the Horowitz email keyserver. Note that your particular installation of GnuPG may have other keyserver types available as well. Most keyservers synchronize with each other, so there is generally no need to send keys to more 11 gpg(1) gpg(1) than one server. Using the command "host -l pgp.net | grep wwwkeys" gives you a list of HKP keyservers. When using one of the wwwkeys servers, due to load balancing using round-robin DNS you may notice that you get a different key server each time. --keyserver-options parameters This is a space or comma delimited string that gives options for the keyserver. Options can be prepended with a `no-' to give the opposite meaning. While not all options are available for all keyserver types, some common options are: include-revoked When receiving or searching for a key, include keys that are marked on the keyserver as revoked. Note that this option is always set when using the NAI HKP keyserver, as this keyserver does not differentiate between revoked and unrevoked keys. include-disabled When receiving or searching for a key, include keys that are marked on the keyserver as disabled. Note that this option is not used with HKP key­ servers, as they do not support dis­ abling keys. 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 commu­ nicate. 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 verbose. This option can be repeated multiple times to increase the verbosity level. 12 gpg(1) gpg(1) honor-http-proxy For keyserver schemes that use HTTP (such as HKP), try to access the key­ server 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. --show-photos Causes --list-keys, --list-sigs, --list-public- keys, and --list-secret-keys to also display the photo ID attached to a key, if any. See also --photo-viewer. --no-show-photos Resets the --show-photos flag. --photo-viewer string This is the command line that should be run to view a photo ID. "%i" will be expanded to a filename containing the photo. "%I" does the same, except the file will not be deleted once the viewer exits. Other flags are "%k" for the key ID, "%K" for the long key ID, "%f" for the key 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" --show-keyring Causes --list-keys, --list-public-keys, and --list-secret-keys to display the name of the keyring a given key resides on. This is only useful when you're listing a specific key or set of keys. It has no effect when listing all keys. --keyring file Add file to the list of keyrings. If file begins with a tilde and a slash, these are replaced by the HOME directory. If the filename does not contain a slash, it is assumed to be in the home-directory ("~/.gnupg" if --homedir is not used). The filename may be prefixed with a scheme: 13 gpg(1) gpg(1) "gnupg-ring:" is the default one. It might make sense to use it together with --no-default-keyring. --secret-keyring file Same as --keyring but for the secret keyrings. --homedir directory Set the name of the home directory to directory If this option is not used it defaults to "~/.gnupg". It does not make sense to use this in a options file. This also overrides the envi­ ronment variable "GNUPGHOME". --charset name Set the name of the native character set. This is used to convert some strings to proper UTF-8 encoding. Valid values for name are: iso-8859-1 This is the default Latin 1 set. iso-8859-2 The Latin 2 set. koi8-r The usual Russian set (rfc1489). utf-8 Bypass all translations and assume that the OS uses native UTF-8 encod­ ing. --utf8-strings --no-utf8-strings Assume that the arguments are already given as UTF8 strings. The default (--no-utf8-strings) is to assume that arguments are encoded in the character set as specified by --charset. These options affect all following arguments. Both options may be used multiple times. --options file Read options from file and do not try to read them from the default options file in the home­ dir (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. 14 gpg(1) gpg(1) --load-extension name Load an extension module. If name does not con­ tain a slash it is searched in "/usr/local/lib/gnupg" See the manual for more information about extensions. --debug flags Set debugging flags. All flags are or-ed and flags may be given in C syntax (e.g. 0x0042). --debug-all Set all useful debugging flags. --status-fd n Write special status strings to the file descriptor n. See the file DETAILS in the docu­ mentation for a listing of them. --logger-fd n Write log output to file descriptor n and not to stderr. --no-comment Do not write comment packets. This option affects only the generation of secret keys. Please note, that this has nothing to do with the comments in clear text signatures. --comment string Use string as comment string in clear text sig­ natures. The default is not do write a comment 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. --no-version Omit the version string in clear text signa­ tures. --emit-version Force to write the version string in clear text signatures. Use this to overwrite a previous --no-version from a config file. -N, --notation-data name=value Put the name value pair into the signature as notation data. name must consist only of alphanumeric characters, digits or the under­ score; the first character must not be a digit. 15 gpg(1) gpg(1) value may be any printable string; it will be encoded in UTF8, so you should check that your --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). --show-notation Show key signature notations in the --list-sigs or --check-sigs listings. --no-show-notation Do not show key signature notations in the --list-sigs or --check-sigs listings. --set-policy-url string Use string as Policy URL for signatures (rfc2440:5.2.3.19). If you prefix it with an exclamation mark, the policy URL packet will be flagged as critical. --show-policy-url Show any policy URLs set in the --list-sigs or --check-sigs listings. --no-show-policy-url Do not show any policy URLs set in the --list- sigs or --check-sigs listings. --set-filename string Use string as the name of file which is stored in messages. --for-your-eyes-only Set the `for your eyes only' flag in the mes­ sage. This causes GnuPG to refuse to save the file unless the --output option is given, and PGP to use the "secure viewer" with a Tempest- resistant font to display the message. This option overrides --set-filename. --no-for-your-eyes-only Resets the --for-your-eyes-only flag. --use-embedded-filename Try to create a file with a name as embedded in the data. This can be a dangerous option as it allows to overwrite files. --completes-needed n Number of completely trusted users to introduce a new key signer (defaults to 1). --marginals-needed n Number of marginally trusted users to introduce 16 gpg(1) gpg(1) 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 pro­ gram with the command --version yields a list of supported algorithms. If this is not used the cipher algorithm is selected from the prefer­ ences stored with the key. --digest-algo name Use name as message digest algorithm. Running the program with the command --version yields a list of supported algorithms. Please note that using this option may violate the OpenPGP requirement, that a 160 bit hash is to be used for DSA. --s2k-cipher-algo name Use name as the cipher algorithm used to pro­ tect secret keys. The default cipher is BLOWFISH. This cipher is also used for conven­ tional encryption if --cipher-algo is not given. --s2k-digest-algo name Use name as the digest algorithm used to mangle the passphrases. The default algorithm is RIPE- MD-160. This digest algorithm is also used for conventional encryption if --digest-algo is not given. --s2k-mode n Selects how passphrases are mangled. If n is 0 a plain passphrase (which is not recommended) will be used, a 1 (default) adds a salt to the passphrase and a 3 iterates the whole process a couple of times. Unless --rfc1991 is used, this mode is also used for conventional encryption. --simple-sk-checksum Secret keys are integrity protected by using a SHA-1 checksum. This method will be part of an 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 this option bears a security risk. --compress-algo n Use compression algorithm n. Default is 2 which 17 gpg(1) gpg(1) is RFC1950 compression. You may use 1 to use the old zlib version (RFC1951) which is used by PGP. 0 disables compression. The default algorithm may give better results because the window size is not limited to 8K. If this is not used the OpenPGP behavior is used, i.e. the compression algorithm is selected from the preferences; note, that this can't be done if you do not encrypt the data. --disable-cipher-algo name Never allow the use of name as cipher algorithm. The given name will not be checked so that a later loaded algorithm will still get disabled. --disable-pubkey-algo name Never allow the use of name as public key algo­ rithm. 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 sig­ natures. Caching gives a much better perfor­ mance 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 hard­ ware malfunctions which could leak out bits from the secret key. This extra verification needs some time (about 115% for DSA keys), and so this option can be used to disable it. However, due to the fact that the signature creation needs manual interaction, this performance penalty does not matter in most settings. --auto-check-trustdb If GnuPG feels that its information about the Web-of-Trust has to be updated, it automatically runs the --check-trustdb command internally. This may be a time consuming process. --no-auto-check-trustdb Resets the --auto-check-trustdb option. --throw-keyid Do not put the keyid into encrypted packets. 18 gpg(1) gpg(1) This option hides the receiver of the message and is a countermeasure against traffic analy­ sis. 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 cleart­ ext signature option. --escape-from-lines Because some mailers change lines starting with "From " to " 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 sensi­ tive) 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 fingerprints. This flag which tells GnuPG to use exactly that primary or secondary key and don't try to figure out which secondary or primary key to use. RETURN VALUE The program returns 0 if everything was fine, 1 if at least a signature was bad, and other error codes for fatal errors. EXAMPLES gpg -se -r Bob file sign and encrypt for user Bob gpg --clearsign file make a clear text signature gpg -sb file make a detached signature gpg --list-keys user_ID show keys 26 gpg(1) gpg(1) gpg --fingerprint user_ID show fingerprint gpg --verify pgpfile gpg --verify sigfile [files] Verify the signature of the file but do not out­ put the data. The second form is used for detached signatures, where sigfile is the detached signature (either ASCII armored of binary) and [files] are the signed data; if this is not given the name of the file holding the signed data is constructed by cutting off the extension (".asc" or ".sig") of sigfile or by asking the user for the filename. ENVIRONMENT HOME Used to locate the default home directory. GNUPGHOME If set directory used instead of "~/.gnupg". GPG_AGENT_INFO Used to locate the gpg-agent; only honred when --use-agent is set. The value constist 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 overide it. http_proxy Only honored when the 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 27 gpg(1) gpg(1) ~/.gnupg/random_seed used to preserve the internal random pool ~/.gnupg/options May contain options /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 dic­ tionary 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 be giving both filenames on the commandline or using - to specify stdin. BUGS On many systems this program should be installed as setuid(root). This is necessary to lock memory pages. Locking memory pages prevents the operating system from writing memory pages to disk. If you get no warning mes­ sage about insecure memory your operating system supports locking without being root. The program drops root privi­ leges as soon as locked memory is allocated. 28