distrib > Mandriva > 2009.1 > x86_64 > media > main-testing > by-pkgid > 944a14da7f77705ed1f6dd9418a3b642 > files > 35


		    GnuPG and OpenPGP

   See RFC2440 for a description of OpenPGP.  We have an annotated version
   of this RFC online:

  Compatibility Notes
   GnuPG (>=1.0.3) is in compliance with RFC2440 despite these exceptions:

    * (9.2) states that IDEA SHOULD be implemented.  This is not done
      due to patent problems.

   All MAY features are implemented with this exception:

    * multi-part armored messages are not supported.
      MIME (rfc2015) should be used instead.

   Most of the OPTIONAL stuff is implemented.

   There are a couple of options which can be used to override some
   RFC requirements.  This is always mentioned with the description
   of that options.

   A special format of partial packet length exists for v3 packets
   which can be considered to be in compliance with RFC1991;  this
   format is only created if a special option is active.

   GnuPG uses a S2K mode of 101 for GNU extensions to the secret key
   protection algorithms.  This number is not defined in OpenPGP, but
   given the fact that this number is in a range which used at many
   other places in OpenPGP for private/experimenat algorithm identifiers,
   this should be not a so bad choice.	The 3 bytes "GNU" are used
   to identify this as a GNU extension - see the file DETAILS for a
   definition of the used data formats.

  Some Notes on OpenPGP / PGP Compatibility:

     * PGP 5.x does not accept V4 signatures for anything other than
       key material.  The GnuPG option --force-v3-sigs mimics this

     * PGP 5.x does not recognize the "five-octet" lengths in
       new-format headers or in signature subpacket lengths.

     * PGP 5.0 rejects an encrypted session key if the keylength
       differs from the S2K symmetric algorithm. This is a bug in its
       validation function.

     * PGP 5.0 does not handle multiple one-pass signature headers and
       trailers. Signing one will compress the one-pass signed literal
       and prefix a V3 signature instead of doing a nested one-pass

     * When exporting a private key, PGP 2.x generates the header
       BLOCK". All previous versions ignore the implied data type, and
       look directly at the packet data type.

     * In a clear-signed signature, PGP 5.0 will figure out the correct
       hash algorithm if there is no "Hash:" header, but it will reject
       a mismatch between the header and the actual algorithm used. The
       "standard" (i.e. Zimmermann/Finney/et al.) version of PGP 2.x
       rejects the "Hash:" header and assumes MD5. There are a number
       of enhanced variants of PGP 2.6.x that have been modified for
       SHA-1 signatures.

     * PGP 5.0 can read an RSA key in V4 format, but can only recognize
       it with a V3 keyid, and can properly use only a V3 format RSA

     * Neither PGP 5.x nor PGP 6.0 recognize ElGamal Encrypt and Sign
       keys. They only handle ElGamal Encrypt-only keys.

  Parts of this document are taken from:

			 OpenPGP Message Format

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