mirror of
git://git.gnupg.org/gnupg.git
synced 2024-12-24 10:39:57 +01:00
108 lines
4.5 KiB
Plaintext
108 lines
4.5 KiB
Plaintext
GnuPG and OpenPGP
|
|
=================
|
|
|
|
See RFC-4880 for a description of OpenPGP. These notes are older
|
|
than RFC-4880 and refer to the predecessor of the specs (RFC-2440).
|
|
|
|
|
|
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.
|
|
UPDATE: Since version 1.4.13 (or GnuPG 2.x with Libgcrypt 1.6)
|
|
IDEA support has been added to allow decryption of old
|
|
PGP-2 encrypted material.
|
|
|
|
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.
|
|
UPDATE: This support has been removed with version 1.3.6.
|
|
|
|
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 that this number is in a range which is used at many other
|
|
places in OpenPGP for private/experimental algorithm identifiers,
|
|
this should be not a too 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
|
|
behavior.
|
|
|
|
* 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
|
|
signature.
|
|
|
|
* When exporting a private key, PGP 2.x generates the header
|
|
"BEGIN PGP SECRET KEY BLOCK" instead of "BEGIN PGP PRIVATE KEY
|
|
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
|
|
key.
|
|
|
|
* 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
|
|
draft-ietf-openpgp-formats-07.txt
|
|
|
|
|
|
Copyright 1998 by The Internet Society. All Rights Reserved.
|
|
|
|
This document and translations of it may be copied and furnished to
|
|
others, and derivative works that comment on or otherwise explain it
|
|
or assist in its implementation may be prepared, copied, published
|
|
and distributed, in whole or in part, without restriction of any
|
|
kind, provided that the above copyright notice and this paragraph
|
|
are included on all such copies and derivative works. However, this
|
|
document itself may not be modified in any way, such as by removing
|
|
the copyright notice or references to the Internet Society or other
|
|
Internet organizations, except as needed for the purpose of
|
|
developing Internet standards in which case the procedures for
|
|
copyrights defined in the Internet Standards process must be
|
|
followed, or as required to translate it into languages other than
|
|
English.
|
|
|
|
The limited permissions granted above are perpetual and will not be
|
|
revoked by the Internet Society or its successors or assigns.
|