General newbe questions using GnuPG

[Steve M. Fabac, Jr.]

As a newbe, I have scanned the GnuPG FAQ looking for help on the question
of configuring GnuPG for encrypting and exchanging files between GnuPG 1.4.1
and a client site running GPG on AiX.

I am running GnuPG 1.4.1  on my end.

My client running PGP 6.52 on AIX.

I generated my key pair taking the defaults when prompted and 
used gpg --armor --export KeyID > testkey.pub 

In the FAQ, the section 5.1 (shown below) has no corresponding section on
"How can I encrypt a message with PGP so that GnuPG is able to decrypt it? 

> 5. COMPATIBILITY ISSUES 
> 
> 5.1) How can I encrypt a message with GnuPG so that PGP is able to decrypt it? 

As a newbe, I have not got a clue on what choices to make running 
gpg --gen-key to make the necessary PGP compatible public key.

On my system, I get:

Please select what kind of key you want:
   (1) DSA and Elgamal (default)
   (2) DSA (sign only)
   (5) RSA (sign only)
Your selection? 1
DSA keypair will have 1024 bits.
ELG-E keys may be between 1024 and 4096 bits long.
What keysize do you want? (2048) 

When I provide the key to my client and he uses it to encrypt
a test message using PGP 6.5 on AIX, I get the following 
when I try to decrypt it with GnuPG:

[smf] unix!/u/smf/test $ gpg --decrypt testfile.txt.pgp | head
gpg: [don't know]: invalid packet (ctb=6f)

Additionally: The key pair I generated was a test pair using 
a non existing user name, a random comment, and bogus
e-mail. (This test key is to be replaced with a production
key with appropriate name, comment, and e-mail ID after testing
is complete).  I then imported the test public key on my
office system and signed the public test key with my 
private key for my e-mail ID.  I exported the signed key
with: gpg --armor --export keyid > testkey2.pub and sent it via
email to my client. 

I can only trust that he did the appropriate steps on his 
AIX box to import the key and generate a test encrypted
message. The result of trying to decrypt the test message 
on the production system is shown above. 

When I use the signed public key on my office system to
encrypt a test file and transfer it to the production
system, I can decrypt the message without problem. 

--

                                      Steve Fabac
                                       S.M. Fabac & Associates
                                        816/765-1670