How to read list-packets

[Johan Wevers]

Hello,

Is there somewhere documentation availeble on how to read the output of
gpg --list-packets? I had a problem some days agoo where someone was not
able to read my encrypted mail. The other person was using GnuPG too, and
finally it turned out she forgot to add the IDEA plugin when she upgraded
GnuPG. The output of gpg --list-packets on my encrypted file is below.

  vulcan:~> gpg --list-packets X.txt.asc
  gpg: NOTE: THIS IS A DEVELOPMENT VERSION!
  gpg: It is only intended for test purposes and should NOT be
  gpg: used in a production environment or with production keys!
  :pubkey enc packet: version 3, algo 1, keyid XXXXXXXXXXXXXXXX
          data: [1023 bits]

This is a 1024 bit RSA key, I assume the algo=1 points to RSA. But why list
it here as 1023 bits?

   :pubkey enc packet: version 3, algo 16, keyid F10A0C407A3FE18C
           data: [3071 bits]
           data: [3071 bits]

Same question here: this is a 3072 bits ElGamal key (mine). Why does it
say 3071 bits here?

   You need a passphrase to unlock the secret key for
   user: "Johan Wevers <johanw@vulcan.xs4all.nl>"
   3072-bit ELG-E key, ID 7A3FE18C, created 2000-08-11 (main key ID 9E8C5DDF)

And here it thinks my key is 3072 bits again?

   Enter passphrase:
   :encrypted data packet:
           length: unknown
   gpg: encrypted with 1024-bit RSA key, ID XXXXXXXX, created 1995-10-15
         "XXXX <xxx@xxxx.xx>"
   gpg: encrypted with 3072-bit ELG-E key, ID 7A3FE18C, created 2000-08-11
         "Johan Wevers <johanw@vulcan.xs4all.nl>"
   :compressed packet: algo=1

I assume the algo=1 here points to the compression algorithm? Or does algo
here mean the IDEA cipher?

   :onepass_sig packet: keyid 6D53AF899E8C5DDF
           version 3, sigclass 00, digest 2, pubkey 17, last=1
  :literal data packet:
           mode b, created 1056096871, name="X.txt",
           raw data: 1368 bytes
   :signature packet: algo 17, keyid 6D53AF899E8C5DDF
           version 3, created 1056096871, md5len 5, sigclass 00
           digest algo 2, begin of digest 70 00
           data: [156 bits]
           data: [157 bits]
   gpg: WARNING: message was not integrity protected

This is more understandable for a signature withg my key.

-- 
ir. J.C.A. Wevers         //  Physics and science fiction site:
johanw@vulcan.xs4all.nl   //  http://www.xs4all.nl/~johanw/index.html
PGP/GPG public keys at http://www.xs4all.nl/~johanw/pgpkeys.html