OpenPGP Options - Using the GNU Privacy Guard
Description: Using the GNU Privacy Guard

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#### 3.2.4 OpenPGP protocol specific options.

`-t, --textmode`
`--no-textmode`
  Treat input files as text and store them in the OpenPGP canonical text form with standard "CRLF" line endings. This also sets the necessary flags to inform the recipient that the encrypted or signed data is text and may need its line endings converted back to whatever the local system uses. This option is useful when 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.
`--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 implies `--no-ask-sig-expire`, and unsets `--sig-policy-url`, `--sig-notation`, and `--sig-keyserver-url`, as these features cannot be used with v3 signatures. `--no-force-v3-sigs` disables this option. Defaults to no.
`--force-v4-certs`
`--no-force-v4-certs`
  Always use v4 key signatures even on v3 keys. This option also changes the default hash algorithm for v3 RSA keys from MD5 to SHA-1. `--no-force-v4-certs` disables this option.
`--force-mdc`
  Force the use of encryption with a modification detection code. This is always used with the newer ciphers (those with a blocksize greater than 64 bits), or if all of the recipient keys indicate MDC support in their feature flags.
`--disable-mdc`
  Disable the use of the modification detection code. Note that by using this option, the encrypted message becomes vulnerable to a message modification attack.
`--personal-cipher-preferences string`
  Set the list of personal cipher preferences to `string`. Use `gpg2 --version` to get a list of available algorithms, and use `none` to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked cipher in this list is also used for the `--symmetric` encryption command.
`--personal-digest-preferences string`
  Set the list of personal digest preferences to `string`. Use `gpg2 --version` to get a list of available algorithms, and use `none` to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked digest algorithm in this list is also used when signing without encryption (e.g. `--clearsign` or `--sign`).
`--personal-compress-preferences string`
  Set the list of personal compression preferences to `string`. Use `gpg2 --version` to get a list of available algorithms, and use `none` to set no preference at all. This allows the user to safely override the algorithm chosen by the recipient key preferences, as GPG will only select an algorithm that is usable by all recipients. The most highly ranked compression algorithm in this list is also used when there are no recipient keys to consider (e.g. `--symmetric`).
`--s2k-cipher-algo name`
  Use `name` as the cipher algorithm used to protect secret keys. The default cipher is CAST5. This cipher is also used for 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 number of times (see –s2k-count). Unless `--rfc1991` is used, this mode is also used for conventional encryption.
`--s2k-count n`
  Specify how many times the passphrase mangling is repeated. This value may range between 1024 and 65011712 inclusive. The default is inquired from gpg-agent. Note that not all values in the 1024-65011712 range are legal and if an illegal value is selected, GnuPG will round up to the nearest legal value. This option is only meaningful if `--s2k-mode` is 3.

#### 3.2.5 Compliance options

These options control what GnuPG is compliant to. Only one of these options may be active at a time. Note that the default setting of this is nearly always the correct one. See the INTEROPERABILITY WITH OTHER OPENPGP PROGRAMS section below before using one of these options.

`--gnupg`
  Use standard GnuPG behavior. This is essentially OpenPGP behavior (see `--openpgp`), but with some additional workarounds for common compatibility problems in different versions of PGP. This is the default option, so it is not generally needed, but it may be useful to override a different compliance option in the gpg.conf file.
`--openpgp`
  Reset all packet, cipher and digest options to strict OpenPGP behavior. Use this option to reset all previous options like `--s2k-*`, `--cipher-algo`, `--digest-algo` and `--compress-algo` to OpenPGP compliant values. All PGP workarounds are disabled.
`--rfc4880`
  Reset all packet, cipher and digest options to strict RFC-4880 behavior. Note that this is currently the same thing as `--openpgp`.
`--rfc2440`
  Reset all packet, cipher and digest options to strict RFC-2440 behavior.
`--rfc1991`
  Try to be more RFC-1991 (PGP 2.x) compliant.
`--pgp2`
  Set up all options to be as PGP 2.x compliant as possible, and warn if an action is taken (e.g. encrypting to a non-RSA key) that will create a message that PGP 2.x will not be able to handle. Note that `PGP 2.x' here means `MIT PGP 2.6.2'. There are other versions of PGP 2.x available, but the MIT release is a good common baseline.

  This option implies `--rfc1991 --disable-mdc --no-force-v4-certs --escape-from-lines --force-v3-sigs --cipher-algo IDEA --digest-algo MD5 --compress-algo ZIP`. It also disables `--textmode` when encrypting.

`--pgp6`
  Set up all options to be as PGP 6 compliant as possible. This restricts you to the ciphers IDEA (if the IDEA plugin is installed), 3DES, and CAST5, the hashes MD5, SHA1 and RIPEMD160, and the compression algorithms none and ZIP. This also disables –throw-keyids, and making signatures with signing subkeys as PGP 6 does not understand signatures made by signing subkeys.

  This option implies `--disable-mdc --escape-from-lines --force-v3-sigs`.

`--pgp7`
  Set up all options to be as PGP 7 compliant as possible. This is identical to `--pgp6` except that MDCs are not disabled, and the list of allowable ciphers is expanded to add AES128, AES192, AES256, and TWOFISH.
`--pgp8`
  Set up all options to be as PGP 8 compliant as possible. PGP 8 is a lot closer to the OpenPGP standard than previous versions of PGP, so all this does is disable `--throw-keyids` and set `--escape-from-lines`. All algorithms are allowed except for the SHA224, SHA384, and SHA512 digests.