gpg

 
 gpg
 ***
 
 Name
 ****
 
 gpg -- encryption and signing tool
 
 Synopsis
 ********
 
      gpg
       --homedir name
       --options file
       options
       command
       args
 
 DESCRIPTION
 ***********
 
 `gpg' is the main program for the GnuPG system.
 
    This man page only lists the commands and options available. For more
 verbose documentation get the GNU Privacy Handbook (GPH) or one of the
 other documents at http://www.gnupg.org/documentation/ .
 
    Please remember that option parsing stops as soon as a non option is
 encountered, you can explicitly stop option parsing by using the
 special option "-".
 
 COMMANDS
 ********
 
 `gpg' may be run with no commands, in which case it will perform a
 reasonable action depending on the type of file it is given as input
 (an encrypted message is decrypted, a signature is verified, a file
 containing keys is listed).
 
    `gpg' recognizes these commands:
 
 -s, -sign
      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 signature. Clear text signatures may modify
      end-of-line whitespace for platform independence and are not
      intended to be reversible.
 
 -b, -detach-sign
      Make a detached signature.
 
 -e, -encrypt
      Encrypt data. This option may be combined with -sign (for a signed
      and encrypted message), -symmetric (for a message that may be
      decrypted via a secret key or a passphrase), or -sign and
      -symmetric together (for a signed message that may be decrypted
      via a secret key or a passphrase).
 
 -c, -symmetric
      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 packet).
 
 -d, -decrypt
      Decrypt `file' (or stdin if no file is specified) and write it to
      stdout (or the file specified with -output). If the decrypted file
      is signed, the signature is also verified. This command differs
      from the default operation, as it never writes to the filename
      which is included in the file and it rejects files which don't
      begin with an encrypted message.
 
 -verify
      Assume that `sigfile' is a 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
 -list-public-keys
      List all keys from the public keyrings, or just the ones given on
      the command line.
 
      Avoid using the output of this command in scripts or other
      programs as it is likely to change as GnuPG changes. See
      -with-colons for a machine-parseable key listing command that is
      appropriate for use in scripts and other programs.
 
 -K, -list-secret-keys
      List all keys from the secret keyrings, or just the ones given on
      the command line. A '#' after the letters 'sec' means that the
      secret key is not usable (for example, if it was created via
      -export-secret-subkeys).
 
 -list-sigs
      Same as -list-keys, but the signatures are listed too.
 
      For each signature listed, there are several flags in between the
      "sig" tag and keyid. These flags give additional information about
      each signature. From left to right, they are the numbers 1-3 for
      certificate check level (see -ask-cert-level), "L" for a local or
      non-exportable signature (see -lsign-key), "R" for a nonRevocable
      signature (see the -edit-key command "nrsign"), "P" for a signature
      that contains a policy URL (see -cert-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.
 
 -fingerprint
      List all keys with their fingerprints. This is the same output as
      -list-keys but with the additional output of a line with the
      fingerprint. May also be combined with -list-sigs or -check-sigs.
      If this command is given twice, the fingerprints of all secondary
      keys are listed too.
 
 -list-packets
      List only the sequence of packets. This is mainly useful for
      debugging.
 
 -gen-key
      Generate a new key pair. This command is normally only used
      interactively.
 
      There is an experimental feature which allows you to create keys
      in batch mode. See the file `doc/DETAILS' in the source
      distribution on how to use this.
 
 -edit-key `name'
      Present a menu which enables you to do all key related tasks:
 
     sign
           Make a signature on key of user `name' If the key is not yet
           signed by the default user (or the users given with -u), the
           program displays the information of the key again, together
           with its fingerprint and asks whether it should be signed.
           This question is repeated for all users specified with -u.
 
     lsign
           Same as "sign" but the signature is marked as non-exportable
           and will therefore never be used by others. This may be used
           to make keys valid only in the local environment.
 
     nrsign
           Same as "sign" but the signature is marked as non-revocable
           and can therefore never be revoked.
 
     tsign
           Make a trust signature. This is a signature that combines the
           notions of certification (like a regular signature), and
           trust (like the "trust" command). It is generally only useful
           in distinct communities or groups.
 
      Note that "l" (for local / non-exportable), "nr" (for
      non-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 generated.
 
     trust
           Change the owner trust value. This updates the trust-db
           immediately and no save is required.
 
     disable
     enable
           Disable or enable an entire key. A disabled key can not
           normally be used for encryption.
 
     adduid
           Create an alternate user id.
 
     addphoto
           Create a photographic user id. This will prompt for a JPEG
           file that will be embedded into the user ID. Note that a very
           large JPEG will make for a very large key. Also note that
           some programs will display your JPEG unchanged (GnuPG), and
           some programs will scale it to fit in a dialog box (PGP).
 
     deluid
           Delete a user id.
 
     delsig
           Delete a signature.
 
     revuid
           Revoke a user id.
 
     addkey
           Add a subkey to this key.
 
     addcardkey
           Generate a key on a card and add it to this key.
 
     keytocard
           Transfer the selected secret key (or the primary key if no
           key has been selected) to a smartcard. The secret key in the
           keyring will be replaced by a stub if the key could be stored
           successfully on the card and you use the save command later.
           Only 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 command only with
           the corresponding public key and make sure that the file
           given as argument is indeed the backup to restore. You should
           then select 2 to restore as encryption key.  You will first
           be asked to enter the passphrase of the backup key and then
           for the Admin PIN of the card.
 
     delkey
           Remove a subkey.
 
     addrevoker
           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 preferences, without including any implied preferences.
 
     showpref
           More verbose preferences listing for the selected user ID.
           This shows the preferences in effect by including the implied
           preferences of 3DES (cipher), SHA-1 (digest), and
           Uncompressed (compression) if they are not already included
           in the preference list. In addition, the preferred keyserver
           and signature notations (if any) are shown.
 
     setpref `string'
           Set the list of user ID preferences to `string' for all (or
           just the selected) user IDs. Calling 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 calculated trust value.
      Letters are used for the values:
 
     -
           No ownertrust assigned / not yet calculated.
 
     e
           Trust calculation has failed; probably due to an expired key.
 
     q
           Not enough information for calculation.
 
     n
           Never trust this key.
 
     m
           Marginally trusted.
 
     f
           Fully trusted.
 
     u
           Ultimately trusted.
 
 -card-edit
      Present a menu to work with a smartcard. The subcommand "help"
      provides an overview on available commands. For a detailed
      description, please see the Card HOWTO at
      http://www.gnupg.org/documentation/howtos.html#GnuPG-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.
 
 -sign-key `name'
      Signs a public key with your secret key. This is a shortcut
      version of the subcommand "sign" from -edit.
 
 -lsign-key `name'
      Signs a public key with your secret key but marks it as
      non-exportable. This is a shortcut version of the subcommand
      "lsign" from -edit.
 
 -delete-key `name'
      Remove key from the public keyring. In batch mode either -yes is
      required or the key must be specified by fingerprint. This is a
      safeguard against accidental deletion of multiple keys.
 
 -delete-secret-key `name'
      Remove key from the secret and public keyring. In batch mode the
      key must be specified by fingerprint.
 
 -delete-secret-and-public-key `name'
      Same as -delete-key, but if a secret key exists, it will be removed
      first. In batch mode the key must be specified by fingerprint.
 
 -gen-revoke `name'
      Generate a revocation certificate for the complete key. To revoke
      a subkey or a signature, use the -edit command.
 
 -desig-revoke `name'
      Generate a designated revocation certificate for a key. This
      allows a user (with the permission of the keyholder) to revoke
      someone else's key.
 
 -export
      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
      Same as -export but sends the keys to a keyserver.  Option
      -keyserver must be used to give the name of this keyserver. Don't
      send your complete keyring to a keyserver - select only those keys
      which are new or changed by you.
 
 -export-secret-keys
 -export-secret-subkeys
      Same as -export, but exports the secret keys instead.  This is
      normally not very useful and a security risk.  The second form of
      the command has the special property to render the secret part of
      the primary key useless; this is a GNU extension to OpenPGP and
      other implementations can not be expected to 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. Calling this with no arguments will
      refresh the entire keyring. Option -keyserver must be used to give
      the name of the keyserver for all keys that do not have preferred
      keyservers set (see -keyserver-options honor-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 processing is identical to that of -update-trustdb but it
      skips keys with a not yet defined "ownertrust".
 
      For use with cron jobs, this command can be used together with
      -batch in which case the trust database check is done only if a
      check is needed. To force a run even in batch mode add the option
      -yes.
 
 -export-ownertrust
      Send the ownertrust values to stdout. This is useful for backup
      purposes as these values are the only ones which can't be
      re-created from a corrupted trust DB.
 
 -import-ownertrust
      Update the trustdb with the ownertrust values stored in `files'
      (or stdin if not given); existing values will be overwritten.
 
 -rebuild-keydb-caches
      When updating from version 1.0.6 to 1.0.7 this command should be
      used to create signature caches in the keyring. It might be handy
      in other situations too.
 
 -print-md `algo'
 -print-mds
      Print message digest of algorithm ALGO for all given files or
      stdin.  With the second form (or a deprecated "*" as algo) digests
      for all available algorithms are printed.
 
 -gen-random `0|1|2'
      Emit COUNT random bytes of the given quality level. If count is
      not given or zero, an endless sequence of random bytes will be
      emitted.  PLEASE, don't use this command unless you know what you
      are doing; it may remove precious entropy from the system!
 
 -gen-prime `mode'  `bits'
      Use the source, Luke :-). The output format is still subject to
      change.
 
 -version
      Print version information along with a list of supported
      algorithms.
 
 -warranty
      Print warranty information.
 
 -h, -help
      Print usage information. This is a really long list even though it
      doesn't list all options. For every option, consult this manual.
 
 OPTIONS
 *******
 
 Long options can be put in an options file (default
 "~/.gnupg/gpg.conf"). Short option names will not work - for example,
 "armor" is a valid option for the options file, while "a" is not. Do
 not write the 2 dashes, but simply the name of the option and any
 required arguments. Lines with a hash ('#') as the first
 non-white-space character are ignored. Commands may be put in this file
 too, but that is not generally useful as the command will execute
 automatically with every execution of gpg.
 
    `gpg' recognizes these options:
 
 -a, -armor
      Create ASCII armored output.
 
 -o, -output `file'
      Write output to `file'.
 
 -max-output `n'
      This option sets a limit on the number of bytes that will be
      generated when processing a file. Since OpenPGP supports various
      levels of compression, it is possible that the 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".
 
 -mangle-dos-filenames
 -no-mangle-dos-filenames
      Older version of Windows cannot handle filenames with more than one
      dot. -mangle-dos-filenames causes GnuPG to replace (rather than add
      to) the extension of an output filename to avoid this problem. This
      option is off by default and has no effect on non-Windows
      platforms.
 
 -u, -local-user `name'
      Use `name' as the key to sign with. Note that this option
      overrides -default-key.
 
 -default-key `name'
      Use `name' as the default key to sign with. If this option is not
      used, the default key is the first key found in the secret keyring.
      Note that -u or -local-user overrides this option.
 
 -r, -recipient `name'
      Encrypt for user id `name'. If this option or -hidden-recipient is
      not specified, GnuPG asks for the user-id unless
      -default-recipient is given.
 
 -R, -hidden-recipient `name'
      Encrypt for user ID `name', but hide the key ID of this user's
      key. This option helps to hide the receiver of the message and is a
      limited countermeasure against traffic analysis. If this option or
      -recipient is not specified, GnuPG asks for the user ID unless
      -default-recipient is given.
 
 -default-recipient `name'
      Use `name' as default recipient if option -recipient is not used
      and don't ask if this is a valid one. `name' must be non-empty.
 
 -default-recipient-self
      Use the default key as default recipient if option -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.
 
 -encrypt-to `name'
      Same as -recipient but this one is intended for use in the options
      file and may be used with your own user-id as an
      "encrypt-to-self". These keys are only used when there are other
      recipients given either by use of -recipient or by the asked user
      id.  No trust checking is performed for these user ids and even
      disabled keys can be used.
 
 -hidden-encrypt-to `name'
      Same as -hidden-recipient but this one is intended for use in the
      options file and may be used with your own user-id as a hidden
      "encrypt-to-self". These keys are only used when there are other
      recipients given either by use of -recipient or by the asked user
      id.  No trust checking is performed for these user ids and even
      disabled keys can be used.
 
 -no-encrypt-to
      Disable the use of all -encrypt-to and -hidden-encrypt-to keys.
 
 -v, -verbose
      Give more information during processing. If used twice, the input
      data is listed in detail.
 
 -q, -quiet
      Try to be as quiet as possible.
 
 -z `n'
 -compress-level `n'
 -bzip2-compress-level `n'
      Set compression level to `n' for the ZIP and ZLIB compression
      algorithms. The default is to use the default compression level of
      zlib (normally 6). -bzip2-compress-level sets the compression level
      for the BZIP2 compression algorithm (defaulting to 6 as well). This
      is a different option from -compress-level since BZIP2 uses a
      significant amount of memory for each additional compression level.
      -z sets both. A value of 0 for `n' disables compression.
 
 -bzip2-decompress-lowmem
      Use a different decompression method for BZIP2 compressed files.
      This alternate method uses a bit more than half the memory, but
      also runs at half the speed. This is useful under extreme low
      memory circumstances when the file was originally compressed at a
      high -bzip2-compress-level.
 
 -t, -textmode
 -no-textmode
      Treat input files as text and store them in the OpenPGP canonical
      text form with standard "CRLF" line endings. This also sets the
      necessary flags to inform the recipient that the encrypted or
      signed data is text and may need its line endings converted back
      to whatever the local system uses. This option is useful when
      communicating between two 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.
 
 -n, -dry-run
      Don't make any changes (this is not completely implemented).
 
 -i, -interactive
      Prompt before overwriting any files.
 
 -batch
 -no-batch
      Use batch mode. Never ask, do not allow interactive 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 if -batch is used.
 
 -yes
      Assume "yes" on most questions.
 
 -no
      Assume "no" on most questions.
 
 -ask-cert-level
 -no-ask-cert-level
      When making a key signature, prompt for a certification level. If
      this option is not specified, the certification level used is set
      via -default-cert-level. See -default-cert-level for information
      on the specific levels and how they are used. -no-ask-cert-level
      disables this option. This option defaults to no.
 
 -default-cert-level `n'
      The default to use for the check level when signing a key.
 
      0 means you make no particular claim as to how carefully you
      verified the key.
 
      1 means you believe the key is owned by the person who claims to
      own it but you could not, or did not verify the key at all. This is
      useful for a "persona" verification, where you sign the key of a
      pseudonymous user.
 
      2 means you did casual verification of the key. For example, this
      could mean that you verified that the key fingerprint and checked
      the user ID on the key against a photo ID.
 
      3 means you did extensive verification of the key. For example,
      this could mean that you verified the key fingerprint with the
      owner of the key in person, and that you checked, by means of a
      hard to forge document with a photo ID (such as a passport) that
      the name of the key owner matches the name in the user ID on the
      key, and finally that you verified (by exchange of email) that the
      email address on the key belongs to the key owner.
 
      Note that the examples given above for levels 2 and 3 are just
      that: examples. In the end, it is up to you to decide just what
      "casual" and "extensive" mean to you.
 
      This option defaults to 0 (no particular claim).
 
 -min-cert-level
      When building the trust database, treat any signatures with a
      certification level below this as invalid. Defaults to 2, which
      disregards level 1 signatures. Note that level 0 "no particular
      claim" signatures are always accepted.
 
 -trusted-key `long key ID'
      Assume that the specified key (which must be given as a full 8
      byte key ID) is as trustworthy as one of your own secret keys.
      This option is useful if you 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 signature checks when
           there is no evidence that the user ID is bound to the key.
 
     auto
           Select the trust model depending on whatever the internal
           trust database says. This is the default model if such a
           database already exists.
 
 -always-trust
      Identical to `-trust-model always'. This option is deprecated.
 
 -auto-key-locate `parameters'
 -no-auto-key-locate
      GnuPG can automatically locate and retrieve keys as needed using
      this option. This happens when encrypting to an email address (in
      the "user@example.com" form), and there are no user@example.com
      keys on the local keyring. This option takes any number of the
      following arguments, in the order they are to be tried:
 
     cert
           locate a key using DNS CERT, as specified in 2538bis
           (currently in draft): http://www.josefsson.org/rfc2538bis/
 
     pka
           locate a key using DNS PKA.
 
     ldap
           locate a key using the PGP Universal method of checking
           "ldap://keys.(thedomain)".
 
     keyserver
           locate a key using whatever keyserver is defined using the
           -keyserver option.
 
     (keyserver URL)
           In addition, a keyserver URL as used in the -keyserver option
           may be used here to query that particular 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 meaningless. Note also
           that most keyservers do not have cryptographic verification
           of key revocations, and so turning this option off may result
           in skipping keys that are incorrectly marked as revoked.
 
     include-disabled
           When searching for a key with -search-keys, include keys that
           are marked on the keyserver as disabled. Note that this
           option is not used with HKP keyservers.
 
     auto-key-retrieve
           This option enables the automatic retrieving of keys from a
           keyserver when verifying signatures made by keys that are not
           on the local keyring.
 
           Note that this option makes a "web bug" like behavior
           possible.  Keyserver operators can see which keys you
           request, so by sending you a message signed by a brand new
           key (which you naturally will not have on your local
           keyring), the operator can tell both your IP address and the
           time when you verified the signature.
 
     honor-keyserver-url
           When using -refresh-keys, if the key in question has a
           preferred keyserver URL, then use that preferred keyserver to
           refresh the key from. In addition, if auto-key-retrieve is
           set, and the signature being verified has a preferred
           keyserver URL, then use that preferred 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 reading the temporary files.
 
     verbose
           Tell the keyserver helper program to be more verbose. This
           option can be repeated multiple times to increase the
           verbosity level.
 
     timeout
           Tell the keyserver helper program how long (in seconds) to
           try and perform a keyserver action before giving up. Note
           that performing multiple actions at the same time uses this
           timeout value per action.  For example, when retrieving
           multiple keys via -recv-keys, the timeout applies separately
           to each key retrieval, and not to the -recv-keys command as a
           whole. Defaults to 30 seconds.
 
     http-proxy
           For HTTP-like keyserver schemes that (such as HKP and HTTP
           itself), try to access the keyserver over a proxy. If a
           `value' is specified, use this as the HTTP proxy. If no
           `value' is specified, the value of the environment variable
           "http_proxy", if any, will be used.
 
     max-cert-size
           When retrieving a key via DNS CERT, only accept keys up to
           this size.  Defaults to 16384 bytes.
 
 -import-options `parameters'
      This is a space or comma delimited string that gives options for
      importing keys. Options can be prepended with a `no-' to give the
      opposite meaning. The options are:
 
     import-local-sigs
           Allow importing key signatures marked as "local". This is not
           generally useful unless a shared keyring scheme is being used.
           Defaults to no.
 
     repair-pks-subkey-bug
           During import, attempt to repair the damage caused by the PKS
           keyserver bug (pre version 0.9.6) that mangles keys with
           multiple subkeys. Note that this cannot completely repair the
           damaged key as some crucial data is removed by the keyserver,
           but it does at least give you back one subkey. Defaults to no
           for regular -import and to yes for keyserver -recv-keys.
 
     merge-only
           During import, allow key updates to existing keys, but do not
           allow any new keys to be imported. Defaults to no.
 
     import-clean
           After import, compact (remove all signatures except the
           self-signature) any user IDs from the new key that are not
           usable.  Then, remove any signatures from the new key that
           are not usable.  This includes signatures that were issued by
           keys that are not present on the keyring. This option is the
           same as running the -edit-key command "clean" after import.
           Defaults to no.
 
     import-minimal
           Import the smallest key possible. This removes all signatures
           except the most recent self-signature on each user ID. This
           option is the same as running the -edit-key command
           "minimize" after import.  Defaults to no.
 
 -export-options `parameters'
      This is a space or comma delimited string that gives options for
      exporting keys. Options can be prepended with a `no-' to give the
      opposite meaning. The options are:
 
     export-local-sigs
           Allow exporting key signatures marked as "local". This is not
           generally useful unless a shared keyring scheme is being used.
           Defaults to no.
 
     export-attributes
           Include attribute user IDs (photo IDs) while exporting. This
           is useful to export keys if they are going to be used by an
           OpenPGP program that does not accept attribute user IDs.
           Defaults to yes.
 
     export-sensitive-revkeys
           Include designated revoker information that was marked as
           "sensitive". Defaults to no.
 
     export-reset-subkey-passwd
           When using the "-export-secret-subkeys" command, this option
           resets the passphrases for all exported subkeys to empty.
           This is useful when the exported subkey is to be used on an
           unattended machine where a passphrase doesn't necessarily
           make sense. Defaults to no.
 
     export-clean
           Compact (remove all signatures from) user IDs on the key being
           exported if the user IDs are not usable. Also, do not export
           any signatures that are not usable. This includes signatures
           that were issued by keys that are not present on the keyring.
           This option is the same as running the -edit-key command
           "clean" before export except that the local copy of the key
           is not modified. Defaults to no.
 
     export-minimal
           Export the smallest key possible. This removes all signatures
           except the most recent self-signature on each user ID. This
           option is the same as running the -edit-key command
           "minimize" before export except that the local copy of the
           key is not modified. Defaults to no.
 
 -list-options `parameters'
      This is a space or comma delimited string that gives options used
      when listing keys and signatures (that is, -list-keys, -list-sigs,
      -list-public-keys, -list-secret-keys, and the -edit-key functions).
      Options can be prepended with a `no-' to give the opposite meaning.
      The options are:
 
     show-photos
           Causes -list-keys, -list-sigs, -list-public-keys, and
           -list-secret-keys to display any photo IDs attached to the
           key.  Defaults to no. See also -photo-viewer.
 
     show-policy-urls
           Show policy URLs in the -list-sigs or -check-sigs listings.
           Defaults to no.
 
     show-notations
     show-std-notations
     show-user-notations
           Show all, IETF standard, or user-defined signature notations
           in the -list-sigs or -check-sigs listings. Defaults to no.
 
     show-keyserver-urls
           Show any preferred keyserver URL in the -list-sigs or
           -check-sigs listings. Defaults to no.
 
     show-uid-validity
           Display the calculated validity of user IDs during key
           listings.  Defaults to no.
 
     show-unusable-uids
           Show revoked and expired user IDs in key listings. Defaults
           to no.
 
     show-unusable-subkeys
           Show revoked and expired subkeys in key listings. Defaults to
           no.
 
     show-keyring
           Display the keyring name at the head of key listings to show
           which keyring a given key resides on. Defaults to no.
 
     show-sig-expire
           Show signature expiration dates (if any) during -list-sigs or
           -check-sigs listings. Defaults to no.
 
     show-sig-subpackets
           Include signature subpackets in the key listing. This option
           can take an optional argument list of the subpackets to list.
           If no argument is passed, list all subpackets. Defaults to
           no. This option is only meaningful when using -with-colons
           along with -list-sigs or -check-sigs.
 
 -verify-options `parameters'
      This is a space or comma delimited string that gives options used
      when verifying signatures. Options can be prepended with a `no-'
      to give the opposite meaning. The options are:
 
     show-photos
           Display any photo IDs present on the key that issued the
           signature.  Defaults to no. See also -photo-viewer.
 
     show-policy-urls
           Show policy URLs in the signature being verified. Defaults to
           no.
 
     show-notations
     show-std-notations
     show-user-notations
           Show all, IETF standard, or user-defined signature notations
           in the signature being verified. Defaults to IETF standard.
 
     show-keyserver-urls
           Show any preferred keyserver URL in the signature being
           verified.  Defaults to no.
 
     show-uid-validity
           Display the calculated validity of the user IDs on the key
           that issued the signature. Defaults to no.
 
     show-unusable-uids
           Show revoked and expired user IDs during signature
           verification.  Defaults to no.
 
     pka-lookups
           Enable PKA lookups to verify sender addresses. Note that PKA
           is based on DNS, and so enabling this option may disclose
           information on when and what signatures are verified or to
           whom data is encrypted. This is similar to the "web bug"
           described for the auto-key-retrieve feature.
 
     pka-trust-increase
           Raise the trust in a signature to full if the signature
           passes PKA validation. This option is only meaningful if
           pka-lookups is set.
 
 -enable-dsa2
 -disable-dsa2
      Enables new-style DSA keys which (unlike the old style) may be
      larger than 1024 bit and use hashes other than SHA-1 and
      RIPEMD/160. Note that very few programs currently support these
      keys and signatures from them.
 
 -show-photos
 -no-show-photos
      Causes -list-keys, -list-sigs, -list-public-keys,
      -list-secret-keys, and verifying a signature to also display the
      photo ID attached to the key, if any. See also -photo-viewer. These
      options are deprecated. Use `-list-options [no-]show-photos' and/or
      `-verify-options [no-]show-photos' instead.
 
 -photo-viewer `string'
      This is the command line that should be run to view a photo ID.
      "%i" will be expanded to a filename containing the photo. "%I"
      does the same, except the file will not be deleted once the viewer
      exits.  Other flags are "%k" for the key ID, "%K" for the long key
      ID, "%f" for the key 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.
 
 -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.
 
 -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 `directory'
      Set the name of the home directory to `directory' If this option
      is not used it defaults to "~/.gnupg". It does not make sense to
      use this in a options file. This also overrides the environment
      variable $GNUPGHOME.
 
 -pcsc-driver `file'
      Use `file' to access the smartcard reader. The current default is
      `libpcsclite.so.1' for GLIBC based systems,
      `/System/Library/Frameworks/PCSC.framework/PCSC' for MAC OS X,
      `winscard.dll' for Windows and `libpcsclite.so' for other systems.
 
 -ctapi-driver `file'
      Use `file' to access the smartcard reader. The current default is
      `libtowitoko.so'. Note that the use of this interface is
      deprecated; it may be removed in future releases.
 
 -disable-ccid
      Disable the integrated support for CCID compliant readers. This
      allows to fall back to one of the other drivers even if the
      internal CCID driver can handle the reader. Note, that CCID
      support is only available if libusb was available at build time.
 
 -reader-port `number_or_string'
      This option may be used to specify the port of the card 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 informational strings like user IDs to the proper UTF-8
      encoding.  Note that this has nothing to do with the character set
      of data to be encrypted or signed; GnuPG does not recode user
      supplied data. If this option is not used, the default character
      set is determined from the current locale. A verbosity level of 3
      shows the chosen set.  Valid values for `name' are:
 
     iso-8859-1
           This is the Latin 1 set.
 
     iso-8859-2
           The Latin 2 set.
 
     iso-8859-15
           This is currently an alias for the Latin 1 set.
 
     koi8-r
           The usual Russian set (rfc1489).
 
     utf-8
           Bypass all translations and assume that the OS uses native
           UTF-8 encoding.
 
 -utf8-strings
 -no-utf8-strings
      Assume that command line arguments are given as UTF8 strings. The
      default (-no-utf8-strings) is to assume that arguments are encoded
      in the character set as specified by -display-charset. These
      options affect all following arguments. Both options may be used
      multiple times.
 
 -options `file'
      Read options from `file' and do not try to read them from the
      default options file in the homedir (see -homedir). This option is
      ignored if used in an options file.
 
 -no-options
      Shortcut for "-options /dev/null". This option is detected before
      an attempt to open an option file.  Using this option will also
      prevent the creation of a "~./gnupg" homedir.
 
 -load-extension `name'
      Load an extension module. If `name' does not contain a slash it is
      searched for in the directory configured when GnuPG was built
      (generally "/usr/local/lib/gnupg"). Extensions are not generally
      useful anymore, and the use of this option is deprecated.
 
 -debug `flags'
      Set debugging flags. All flags are or-ed and `flags' may be given
      in C syntax (e.g. 0x0042).
 
 -debug-all
      Set all useful debugging flags.
 
 -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 performance overhead using it.
 
 -status-fd `n'
      Write special status strings to the file descriptor `n'.  See the
      file DETAILS in the documentation for a listing of them.
 
 -status-file `file'
      Same as -status-fd, except the status data is written to file
      `file'.
 
 -logger-fd `n'
      Write log output to file descriptor `n' and not to stderr.
 
 -logger-file `file'
      Same as -logger-fd, except the logger data is written to file
      `file'.
 
 -attribute-fd `n'
      Write attribute subpackets to the file descriptor `n'. This is
      most useful for use with -status-fd, since the status messages are
      needed to separate out the various subpackets from the stream
      delivered to the file descriptor.
 
 -attribute-file `file'
      Same as -attribute-fd, except the attribute data is written to file
      `file'.
 
 -comment `string'
 -no-comments
      Use `string' as a comment string in clear text signatures and
      ASCII armored messages or keys (see -armor). The default behavior
      is not to use a comment string. -comment may be repeated multiple
      times to get multiple comment strings. -no-comments removes all
      comments.  It is a good idea to keep the length of a single
      comment below 60 characters to avoid problems with mail programs
      wrapping such lines.  Note that comment lines, like all other
      header lines, are not protected by the signature.
 
 -emit-version
 -no-emit-version
      Force inclusion of the version string in ASCII armored output.
      -no-emit-version disables this option.
 
 -sig-notation `name=value'
 -cert-notation `name=value'
 -N, -set-notation `name=value'
      Put the name value pair into the signature as notation data.
      `name' must consist only of printable characters or spaces, and
      must contain a '@' character in the form keyname@domain.example.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 (certifications). -set-notation sets both.
 
      There are special codes that may be used in notation names. "%k"
      will be expanded into the key ID of the key being signed, "%K"
      into the long key ID of the key being signed, "%f" into the
      fingerprint of the key being signed, "%s" into the key ID of the
      key making the signature, "%S" into the long key ID of the key
      making the signature, "%g" into the fingerprint of the key making
      the signature (which might be a subkey), "%p" into the fingerprint
      of the primary key of the key making the signature, "%c" into the
      signature count from the OpenPGP smartcard, and "%%" results in a
      single "%". %k, %K, and %f are only meaningful when making a key
      signature (certification), and %c is only meaningful when using
      the OpenPGP smartcard.
 
 -show-notation
 -no-show-notation
      Show signature notations in the -list-sigs or -check-sigs listings
      as well as when verifying a signature with a notation in it. These
      options are deprecated. Use `-list-options [no-]show-notation'
      and/or `-verify-options [no-]show-notation' instead.
 
 -sig-policy-url `string'
 -cert-policy-url `string'
 -set-policy-url `string'
      Use `string' as a Policy URL for signatures (rfc2440:5.2.3.19).
      If you prefix it with an exclamation mark (!), the policy URL
      packet will be flagged as critical. -sig-policy-url sets a policy
      url for data signatures. -cert-policy-url sets a policy url for key
      signatures (certifications). -set-policy-url sets both.
 
      The same %-expandos used for notation data are available here as
      well.
 
 -show-policy-url
 -no-show-policy-url
      Show policy URLs in the -list-sigs or -check-sigs listings as well
      as when verifying a signature with a policy URL in it. These
      options are deprecated. Use `-list-options [no-]show-policy-url'
      and/or `-verify-options [no-]show-policy-url' instead.
 
 -sig-keyserver-url `string'
      Use `string' as a preferred keyserver URL for data signatures. If
      you prefix it with an exclamation mark, the keyserver URL packet
      will be flagged as critical.
 
      The same %-expandos used for notation data are available here as
      well.
 
 -set-filename `string'
      Use `string' as the filename which is stored inside messages.
      This overrides the default, which is to use the actual 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.
 
 -completes-needed `n'
      Number of completely trusted users to introduce a new key signer
      (defaults to 1).
 
 -marginals-needed `n'
      Number of marginally trusted users to introduce a new key signer
      (defaults to 3)
 
 -max-cert-depth `n'
      Maximum depth of a certification chain (default is 5).
 
 -cipher-algo `name'
      Use `name' as cipher algorithm. Running the program with the
      command -version yields a list of supported algorithms. If this is
      not used the cipher algorithm is selected from the preferences
      stored with the key. In general, you do not want to use this
      option as it allows you to violate the OpenPGP standard.
      -personal-cipher-preferences is the safe way to accomplish the same
      thing.
 
 -digest-algo `name'
      Use `name' as the message digest algorithm. Running the program
      with the command -version yields a list of supported 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 compression scheme that can
      compress some things better than zip or zlib, but at the cost of
      more memory used during compression and decompression.
      "uncompressed" or "none" disables compression. If this option is
      not used, the default behavior is to examine the recipient key
      preferences to see which algorithms the recipient supports. If all
      else fails, ZIP is used for maximum compatibility.
 
      ZLIB may give better compression results than ZIP, as the
      compression window size is not limited to 8k. BZIP2 may give even
      better compression results than that, but will use a significantly
      larger amount of memory while compressing and decompressing. This
      may be significant in low memory 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-compress-preferences is the safe way to accomplish the
      same thing.
 
 -cert-digest-algo `name'
      Use `name' as the message digest algorithm used when signing a
      key. Running the program with the command -version yields a list of
      supported algorithms. Be aware that if you choose an algorithm that
      GnuPG supports but other OpenPGP implementations do not, then some
      users will not be able to use the key signatures you make, or quite
      possibly your entire key.
 
 -s2k-cipher-algo `name'
      Use `name' as the cipher algorithm used to protect secret keys.
      The default cipher is CAST5. This cipher is also used for
      conventional encryption if -personal-cipher-preferences and
      -cipher-algo is not given.
 
 -s2k-digest-algo `name'
      Use `name' as the digest algorithm used to mangle the passphrases.
      The default algorithm is SHA-1.
 
 -s2k-mode `n'
      Selects how passphrases are mangled. If `n' is 0 a plain
      passphrase (which is not recommended) will be used, a 1 adds a
      salt to the passphrase and a 3 (the default) iterates the whole
      process a couple of times. Unless -rfc1991 is used, this mode is
      also used for conventional encryption.
 
 -simple-sk-checksum
      Secret keys are integrity protected by using a SHA-1 checksum. This
      method is part of the upcoming enhanced OpenPGP specification but
      GnuPG already uses it as a countermeasure against certain attacks.
      Old applications don't understand this new format, so this option
      may be used to switch back to the old behaviour. Using this option
      bears a security risk. Note that using this option only takes
      effect when the secret key is encrypted - the simplest way to make
      this happen is to change the passphrase on the key (even changing
      it to the same value is acceptable).
 
 -disable-cipher-algo `name'
      Never allow the use of `name' as cipher algorithm.  The given name
      will not be checked so that a later loaded algorithm will still
      get disabled.
 
 -disable-pubkey-algo `name'
      Never allow the use of `name' as public key algorithm.  The given
      name will not be checked so that a later loaded algorithm will
      still get disabled.
 
 -no-sig-cache
      Do not cache the verification status of key signatures.  Caching
      gives a much better performance in key listings. However, if you
      suspect that your public keyring is not save against write
      modifications, you can use this option to 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 consuming process.
      -no-auto-check-trustdb disables this option.
 
 -throw-keyids
 -no-throw-keyids
      Do not put the recipient key IDs into encrypted messages. This
      helps to hide the receivers of the message and is a limited
      countermeasure against traffic analysis. On the receiving side, it
      may slow down the decryption process because all available secret
      keys must be tried.  -no-throw-keyids disables this option. This
      option is essentially the same as using -hidden-recipient for all
      recipients.
 
 -not-dash-escaped
      This option changes the behavior of cleartext signatures so that
      they can be used for patch files. You should not send such an
      armored file via email because all spaces and line endings are
      hashed too. You can not use this option for data which has 5
      dashes at the beginning of a line, patch files 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-fd `n'
      Read the passphrase from file descriptor `n'. Only the first line
      will be read from file descriptor `n'. If you use 0 for `n', the
      passphrase will be read from stdin. This can only be used if only
      one passphrase is supplied.
 
 -passphrase-file `file'
      Read the passphrase from file `file'. Only the first line will be
      read from file `file'. This can only be used if only one
      passphrase is supplied. Obviously, a passphrase stored in a file is
      of questionable security if other users can read this file. Don't
      use this option if you can avoid it.
 
 -passphrase `string'
      Use `string' as the passphrase. This can only be used if only one
      passphrase is supplied. Obviously, this is of very 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'
 
 -use-agent
 -no-use-agent
      Try to use the GnuPG-Agent. Please note that this agent is still
      under development. With this option, GnuPG first tries to connect
      to the agent before it asks for a passphrase. -no-use-agent
      disables this option.
 
 -gpg-agent-info
      Override the value of the environment variable `GPG_AGENT_INFO'.
      This is only used when -use-agent has been given
 
 Compliance options
      These options control what GnuPG is compliant to. Only one of these
      options may be active at a time. Note that the default setting of
      this is nearly always the correct one. See the INTEROPERABILITY
      WITH OTHER OPENPGP PROGRAMS section below before using one of these
      options.
 
     -gnupg
           Use standard GnuPG behavior. This is essentially OpenPGP
           behavior (see -openpgp), but with some additional workarounds
           for common compatibility problems in different versions of
           PGP. This is the default option, so it is not generally
           needed, but it may be useful to override a different
           compliance option in the gpg.conf file.
 
     -openpgp
           Reset all packet, cipher and digest options to strict OpenPGP
           behavior. Use this option to reset all previous options like
           -rfc1991, -force-v3-sigs, -s2k-*, -cipher-algo, -digest-algo
           and -compress-algo to OpenPGP compliant values. All PGP
           workarounds are disabled.
 
     -rfc2440
           Reset all packet, cipher and digest options to strict RFC-2440
           behavior. Note that this is currently the same thing as
           -openpgp.
 
     -rfc1991
           Try to be more RFC-1991 (PGP 2.x) compliant.
 
     -pgp2
           Set up all options to be as PGP 2.x compliant as possible,
           and warn if an action is taken (e.g. encrypting to a non-RSA
           key) that will create a message that PGP 2.x will not be able
           to handle. Note that `PGP 2.x' here means `MIT PGP 2.6.2'.
           There are other versions of PGP 2.x available, but the MIT
           release is a good common baseline.
 
           This option implies `-rfc1991 -disable-mdc -no-force-v4-certs
           -no-sk-comment -escape-from-lines -force-v3-sigs
           -no-ask-sig-expire -no-ask-cert-expire -cipher-algo IDEA
           -digest-algo MD5 -compress-algo 1'. It also disables -textmode
           when encrypting.
 
     -pgp6
           Set up all options to be as PGP 6 compliant as possible. This
           restricts you to the ciphers IDEA (if the IDEA plugin is
           installed), 3DES, and CAST5, the hashes MD5, SHA1 and
           RIPEMD160, and the compression algorithms none and ZIP. This
           also disables -throw-keyids, and making signatures with
           signing subkeys as PGP 6 does not understand signatures made
           by signing subkeys.
 
           This option implies `-disable-mdc -no-sk-comment
           -escape-from-lines -force-v3-sigs -no-ask-sig-expire'
 
     -pgp7
           Set up all options to be as PGP 7 compliant as possible. This
           is identical to -pgp6 except that MDCs are not disabled, and
           the list of allowable ciphers is expanded to add AES128,
           AES192, AES256, and TWOFISH.
 
     -pgp8
           Set up all options to be as PGP 8 compliant as possible. PGP
           8 is a lot closer to the OpenPGP standard than previous
           versions of PGP, so all this does is disable -throw-keyids
           and set -escape-from-lines.  All algorithms are allowed
           except for the SHA224, SHA384, and SHA512 digests.
 
 -force-v3-sigs
 -no-force-v3-sigs
      OpenPGP states that an implementation should generate v4 signatures
      but PGP versions 5 through 7 only recognize v4 signatures on key
      material. This option forces v3 signatures for signatures on data.
      Note that this option overrides -ask-sig-expire, as v3 signatures
      cannot have expiration dates. -no-force-v3-sigs disables this
      option.
 
 -force-v4-certs
 -no-force-v4-certs
      Always use v4 key signatures even on v3 keys. This option also
      changes the default hash algorithm for v3 RSA keys from MD5 to
      SHA-1.  -no-force-v4-certs disables this option.
 
 -force-mdc
      Force the use of encryption with a modification detection code.
      This is always used with the newer ciphers (those with a blocksize
      greater than 64 bits), or if all of the recipient keys indicate
      MDC support in their feature flags.
 
 -disable-mdc
      Disable the use of the modification detection code. Note that by
      using this option, the encrypted message becomes vulnerable to a
      message modification attack.
 
 -allow-non-selfsigned-uid
 -no-allow-non-selfsigned-uid
      Allow the import and use of keys with user IDs which are not
      self-signed. This is not recommended, as a non self-signed user ID
      is trivial to forge. -no-allow-non-selfsigned-uid disables.
 
 -allow-freeform-uid
      Disable all checks on the form of the user ID while 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.
 
 -lock-once
      Lock the databases the first time a lock is requested and do not
      release the lock until the process terminates.
 
 -lock-multiple
      Release the locks every time a lock is no longer needed. Use this
      to override a previous -lock-once from a config file.
 
 -lock-never
      Disable locking entirely. This option should be used only in very
      special environments, where it can be assured that only one process
      is accessing those files. A bootable floppy with a stand-alone
      encryption system will probably use this. Improper usage of this
      option may lead to data and key corruption.
 
 -exit-on-status-write-error
      This option will cause write errors on the status FD to 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 operations.
 
 -limit-card-insert-tries `n'
      With `n' greater than 0 the number of prompts asking to insert a
      smartcard gets limited to N-1. Thus with a value of 1 gpg 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 infinitum
      for an inserted card.
 
 -no-random-seed-file
      GnuPG uses a file to store its internal random pool over
      invocations.  This makes random generation faster; however
      sometimes write operations are not desired. This option can be
      used to achieve that with the cost of slower random generation.
 
 -no-verbose
      Reset verbose level to 0.
 
 -no-greeting
      Suppress the initial copyright message.
 
 -no-secmem-warning
      Suppress the warning about "using insecure memory".
 
 -no-permission-warning
      Suppress the warning about unsafe file and home directory
      (-homedir) permissions. Note that the permission checks that GnuPG
      performs are not intended to be authoritative, but rather they
      simply warn about certain common permission problems. Do not
      assume that the lack of a warning means that your system is secure.
 
      Note that the warning for unsafe -homedir permissions cannot be
      suppressed in the gpg.conf file, as this would allow an attacker to
      place an unsafe gpg.conf file in place, and use this file to
      suppress warnings about itself. The -homedir permissions warning
      may only be suppressed on the command line.
 
 -no-mdc-warning
      Suppress the warning about missing MDC integrity protection.
 
 -require-secmem
 -no-require-secmem
      Refuse to run if GnuPG cannot get secure memory. Defaults to no
      (i.e. run, but give a warning).
 
 -no-armor
      Assume the input data is not in ASCII armored format.
 
 -no-default-keyring
      Do not add the default keyrings to the list of keyrings. Note that
      GnuPG will not operate without any keyrings, so if you use this
      option and do not provide alternate keyrings via -keyring or
      -secret-keyring, then GnuPG will still use the default public or
      secret keyrings.
 
 -skip-verify
      Skip the signature verification step. This may be used to make the
      decryption faster if the signature verification is not needed.
 
 -with-colons
      Print key listings delimited by colons. Note that the output will
      be encoded in UTF-8 regardless of any -display-charset setting.
      This format is useful when GnuPG is called from scripts and other
      programs as it is easily machine parsed. The details of this
      format are documented in the file doc/DETAILS, which is included
      in the GnuPG source distribution.
 
 -with-key-data
      Print key listings delimited by colons (like -with-colons) and
      print the public key data.
 
 -with-fingerprint
      Same as the command -fingerprint but changes only the format of
      the output and may be used together with another command.
 
 -fast-list-mode
      Changes the output of the list commands to work faster; this is
      achieved by leaving some parts empty. Some applications don't need
      the user ID and the trust information given in the listings. By
      using this options they can get a faster listing. The exact
      behaviour of this option may change in future versions.
 
 -fixed-list-mode
      Do not merge primary user ID and primary key in -with-colon listing
      mode and print all timestamps as seconds since 1970-01-01.
 
 -list-only
      Changes the behaviour of some commands. This is like -dry-run but
      different in some cases. The semantic of this 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.
 
 -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.
 
 -require-cross-certification
 -no-require-certification
      When verifying a signature made from a subkey, ensure that the
      cross certification "back signature" on the subkey is present and
      valid.  This protects against a subtle attack against subkeys that
      can sign.  Currently defaults to -no-require-cross-certification,
      but will be changed to -require-cross-certification in the future.
 
 -ask-sig-expire
 -no-ask-sig-expire
      When making a data signature, prompt for an expiration time. If
      this option is not specified, the expiration time set via
      -default-sig-expire is used. -no-ask-sig-expire disables this
      option. Note that by default, -force-v3-sigs is set which also
      disables this option. If you want signature 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".
 
 -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 incompatible
      actions. As the name implies, this option is for experts only. If
      you don't fully understand the implications of what it allows you
      to do, leave this off. -no-expert disables this option.
 
 -allow-secret-key-import
      This is an obsolete option and is not used anywhere.
 
 -try-all-secrets
      Don't look at the key ID as stored in the message but try all
      secret keys in turn to find the right decryption key. This option
      forces the behaviour as used by anonymous recipients (created by
      using -throw-keyids) and might come handy in case where an
      encrypted message contains a bogus key ID.
 
 -allow-multisig-verification
      Allow verification of concatenated signed messages. This will run a
      signature verification for each data+signature block. There are
      some security issues with this option and thus it is off by
      default. Note that versions of GPG prior to version 1.4.3
      implicitly allowed this.
 
 -enable-special-filenames
      This options enables a mode in which filenames of the form `-&n',
      where n is a non-negative decimal number, refer to the file
      descriptor n and not to a file with that name.
 
 -no-expensive-trust-checks
      Experimental use only.
 
 -group `name=value1 '
      Sets up a named group, which is similar to aliases in email
      programs.  Any time the group name is a recipient (-r or
      -recipient), it will be expanded to the values specified. Multiple
      groups with the same name are automatically merged into a single
      group.
 
      The values are `key IDs' or fingerprints, but any key description
      is accepted. Note that a value with spaces in it will be treated as
      two different values. Note also there is only one level of
      expansion - you cannot make an group that points to another group.
      When used from the command line, it may be necessary to quote the
      argument to this option to prevent the shell from treating it as
      multiple arguments.
 
 -ungroup `name'
      Remove a given entry from the -group list.
 
 -no-groups
      Remove all entries from the -group list.
 
 -preserve-permissions
      Don't change the permissions of a secret keyring back to user
      read/write only. Use this option only if you really know what you
      are doing.
 
 -personal-cipher-preferences `string'
      Set the list of personal cipher preferences to `string', this list
      should be a string similar to the one printed by the command
      "pref" in the edit menu. This allows the user to factor in their
      own preferred algorithms when algorithms are chosen via recipient
      key preferences.  The most highly ranked cipher in this list is
      also used for the -symmetric encryption command.
 
 -personal-digest-preferences `string'
      Set the list of personal digest preferences to `string', this list
      should be a string similar to the one printed by the command
      "pref" in the edit menu. This allows the user to factor in their
      own preferred algorithms when algorithms are chosen via 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', this
      list should be a string similar to the one printed by the command
      "pref" in the edit menu. This allows the user to factor in their
      own preferred algorithms when algorithms are chosen via recipient
      key preferences. The most highly ranked algorithm in this list is
      also used when there are no recipient keys to consider (e.g.
      -symmetric).
 
 -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.
 
 How to specify a user ID
 ************************
 
 There are different ways to specify a user ID to GnuPG; here are some
 examples:
 
 
 
 234567C4
 0F34E556E
 01347A56A
 0xAB123456
      Here the key ID is given in the usual short form.
 
 234AABBCC34567C4
 0F323456784E56EAB
 01AB3FED1347A5612
 0x234AABBCC34567C4
      Here the key ID is given in the long form as used by OpenPGP (you
      can get the long key ID using the option -with-colons).
 
 1234343434343434C434343434343434
 123434343434343C3434343434343734349A3434
 0E12343434343434343434EAB3484343434343434
 0xE12343434343434343434EAB3484343434343434
      The best way to specify a key ID is by using the fingerprint of
      the key. This avoids any ambiguities in case that there are
      duplicated key IDs (which are really rare for the long key IDs).
 
 =Heinrich Heine <heinrichh@uni-duesseldorf.de>
      Using an exact to match string. The equal sign indicates this.
 
 <heinrichh@uni-duesseldorf.de>
      Using the email address part which must match exactly. The left
      angle bracket indicates this email address mode.
 
 @heinrichh
      Match within the <email.address> part of a user ID. The at sign
      indicates this email address mode.
 
 Heine
 *Heine
      By case insensitive substring matching. This is the default mode
      but applications may want to explicitly indicate this by putting
      the asterisk in front.
 
    Note that you can append an exclamation mark (!) to key IDs or
 fingerprints. This flag tells GnuPG to use the specified primary or
 secondary key and not to try and calculate which primary or secondary
 key to use.
 
 RETURN VALUE
 ************
 
 The program returns 0 if everything was fine, 1 if at least a signature
 was bad, and other error codes for fatal errors.
 
 EXAMPLES
 ********
 
 gpg -se -r `Bob' `file'
      sign and encrypt for user Bob
 
 gpg -clearsign `file'
      make a clear text signature
 
 gpg -sb `file'
      make a detached signature
 
 gpg -list-keys `user_ID'
      show keys
 
 gpg -fingerprint `user_ID'
      show fingerprint
 
 gpg -verify `pgpfile'
 gpg -verify `sigfile'
      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.
 
 ENVIRONMENT
 ***********
 
 HOME
      Used to locate the default home directory.
 
 GNUPGHOME
      If set directory used instead of "~/.gnupg".
 
 GPG_AGENT_INFO
      Used to locate the gpg-agent; only honored when -use-agent is set.
      The value consists of 3 colon delimited fields: The first is the
      path to the Unix Domain Socket, the second the PID of the
      gpg-agent and the protocol version which should be set to 1. When
      starting the gpg-agent as described in its documentation, this
      variable is set to the correct value. The option -gpg-agent-info
      can be used to override it.
 
 COLUMNS
 LINES
      Used to size some displays to the full size of the screen.
 
 FILES
 *****
 
 ~/.gnupg/secring.gpg
      The secret keyring
 
 ~/.gnupg/secring.gpg.lock
      and the lock file
 
 ~/.gnupg/pubring.gpg
      The public keyring
 
 ~/.gnupg/pubring.gpg.lock
      and the lock file
 
 ~/.gnupg/trustdb.gpg
      The trust database
 
 ~/.gnupg/trustdb.gpg.lock
      and the lock file
 
 ~/.gnupg/random_seed
      used to preserve the internal random pool
 
 ~/.gnupg/gpg.conf
      Default configuration file
 
 ~/.gnupg/options
      Old style configuration file; only used when gpg.conf is not found
 
 /usr[/local]/share/gnupg/options.skel
      Skeleton options file
 
 /usr[/local]/lib/gnupg/
      Default location for extensions
 
 WARNINGS
 ********
 
 Use a *good* password for your user account and a *good* passphrase to
 protect your secret key. This passphrase is the weakest part of the
 whole system. Programs to do dictionary attacks on your secret keyring
 are very easy to write and so you should protect your "~/.gnupg/"
 directory very well.
 
    Keep in mind that, if this program is used over a network (telnet),
 it is *very* easy to spy out your passphrase!
 
    If you are going to verify detached signatures, make sure that the
 program knows about it; either give both filenames on the command line
 or use `-' to specify stdin.
 
 INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS
 ********************************************
 
 GnuPG tries to be a very flexible implementation of the OpenPGP
 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 violation of
 OpenPGP, but rather reduce the available algorithms to a "PGP-safe"
 list.
 
 BUGS
 ****
 
 On many systems this program should be installed as setuid(root). This
 is necessary to lock memory pages. Locking memory pages prevents the
 operating system from writing memory pages (which may contain
 passphrases or other sensitive material) to disk. If you get no 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.
 
 

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