Problems with compatibility between GnuPG 1.2.2 and PGPTools 7.0.3

Michael Young mwy-gpg41 at
Wed Sep 10 18:45:02 CEST 2003

Hash: SHA1

I think the real issue is:
> :compressed packet: algo=2

Older PGP versions have not supported this compression algorithm
(2 = ZLIB), only the original (1 = ZIP).  

The --pgp7 switch will work.  But, you'll need to remember to use it
every time (or put it in your options file where it will affect *all* of 
your keys), and tell everyone who uses it about this quirk.

The better way to deal with this is to get your key preferences set
appropriately for the system where you'll use the secret key (PGP7 in
your case).  In your case, you might
    gpg --edit-key your_key
 setpref S2 H2 Z1

to set your preferences for:
    ciphers (S2 = 3DES);
    hash function (H2 = SHA-1); and,
    compression (Z1 = ZIP, the PGP-compatible one).

You can choose other ciphers and hash functions, and even put Z2=ZLIB
after Z1 if you like.  My example was intended to be simple, not

Then, if you give your public key to someone else, they won't have to
add any incantations at encryption time.  GPG, PGP, and any other
compliant system should abide by your preferences automatically.

A couple of thoughts for Werner and/or David:
  I understand that ZLIB has some performance benefits, but this
  issue comes up often enough that I question whether it is the right
  default.  Or, perhaps this could be part of the key generation dialog?

  It would also be mighty convenient to be able to set
  the preferences with "--pgp7 --edit-key" followed by "updpref".
  Alternatively, it would be nice to have some macros (like "pgp7")
  that would be recognized in preference lists.

Version: PGP Personal Privacy 6.5.3


More information about the Gnupg-devel mailing list