GnuPG and PGP 5.0 compatibility problem

[David Shaw]

On Fri, Jul 13, 2007 at 10:42:37PM +0200, Stefan Oltmanns wrote:
> Hello,
> 
> I got a problem with GnuPG and PGP 5.0:
> Also PGP 5 accepts my key, it is not possible for PGP 5 to encrypt with 
> my key. It´s not even displayed in the selection dialog when I try to 
> encrypt something (it shows identities correct in key list (but 
> expiration not)).
> 
> I read in the FAQ that PGP 5.0 does not accept ElGamal keys of type 20, 
> but my key doesn´t seem to be of that type (--list-packets says "version 
> 4, algo 16, created 1153340019, expires 0")
> 
> There seem to be another problem, do you have any idea how to solve it?

We'd have to track down what the problem was first.  Understand that
PGP 5.0 predates the OpenPGP standard that modern PGP and GnuPG use by
quite a while.  It's not massively insecure (though there were some
bugs reported), but it just doesn't follow the same "rule book" as
everyone else.

The usual PGP 5 behavior when it doesn't understand something is to
ignore it, as you saw.

David