--openpgp, MDC and similar flags

Christoph Anton Mitterer cam at mathematica.scientia.net
Tue Nov 29 02:28:40 CET 2005


Hi....

I've got some questions ;-)


About the differences between what OpenPGP (RFC2440) specifies and what 
GnuPG does:
1) I've created my key with "openpgp" in the config file,... so 
everything should have been absolutely rfc2440 confomant, right?
Ok, but:
Command> showpref
pub  4096R/5BB9A53D  created: 2005-10-28  expires: never       usage: CS
                     trust: unknown       validity: unknown
[ unknown] (1). Christoph Anton Mitterer
     Cipher: AES256, AES192, AES, CAST5, 3DES
     Digest: SHA1, RIPEMD160
     Compression: ZLIB, ZIP, Uncompressed
     Features: MDC, Keyserver no-modify
[ unknown] (2)  Christoph Anton Mitterer <calestyo at scientia.net>
     Cipher: AES256, AES192, AES, CAST5, 3DES
     Digest: SHA1, RIPEMD160
     Compression: ZLIB, ZIP, Uncompressed
     Features: MDC, Keyserver no-modify
[ unknown] (3)  Christoph Anton Mitterer 
<mail at christoph.anton.mitterer.name>
     Cipher: AES256, AES192, AES, CAST5, 3DES
     Digest: SHA1, RIPEMD160
     Compression: ZLIB, ZIP, Uncompressed
     Features: MDC, Keyserver no-modify

... as you can see, MDC is set. Referring to 
http://lists.gnupg.org/pipermail/gnupg-users/2003-May/018442.html and 
RFC2440 I assume that MDC is still not part of the standard. Why is it 
activated in my key? (Of course this is a good thing, but I just wonder 
that if "openpgp" did not work for MDC, other things might be 
"incompatible", too)


2) What other things does GPG that are beyond RFC2440?
a) I've had that discussion with David about backsignatures which use 
0x19 sigs or so (he didn't answer yet, so I'm not sure if this is 
RFC2440 compliant).
b) rfc 2440 seems to specify values only for MD5 and SHA1 but not for 
SHAxxx, RIPEMD160, etc. same thing with AESxxx and other modern 
symmetric algorithms. Same thing with bzip2.
=> Are these things standardized or not? If not yet, is the working 
groupt on OpenPGP going to use the same values as GPG uses? What if not?
If some have been already standardized: Where? *G*
=> Any other things like this, where GPG goes beyond rfc2440?

(btw: can PGP (the commercial one) open signatures/messages using AESxxx 
as cipher and SHAxxx as hash?)


3) Are there any other flags like MDC? I know about keyserver-no-modify 
but that is documented in RFC2440.



4) Does GnuPG support 0x10 (private key split) and 0x80 (group key) for 
the key usage flag?


Best wishes,
Chris.
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