Now I remember why I linked Crypt OpenPGP Brain twister, its a Short, Self Contained, Correct Example, in otherwords, more effective :)

If you modify Crypt-OpenPGP-1.06\t\12-sign.t at the first verify call, you can see that this is to be expected

    my( $signer , $sigobj ) = $pgp->verify( Signature => $sig );
    use DDS; die Dump( [ $key_id , $sigobj->key_id, unpack('H*', $sigo
+bj->key_id ) , pack('H*',$key_id) ] );
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$ARRAY1 = [
            '39F560A90D7F1559',
            "9\365`\251\r\177\25Y",
            '39f560a90d7f1559',
            "9\365`\251\r\177\25Y"
          ];
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I don't know if keyid is supposed to be 8 or 10 or 16, but the round trip with pack seems to work , so key_id is correct, and the hex representation is correct

AFAIK printf would actually try to convert it, which might overflow as in

$ perl -le " print 0x39f560a90d7f1559
Integer overflow in hexadecimal number at -e line 1.
4.17635050864817e+018
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Maybe this is the private key, and you're looking for the public key? Maybe it depends on algorithm? :)

Thank you! A combo of your posts and some further reading on key id formats did it:

http://search.cpan.org/grep?cpanid=BTROTT&release=Crypt-OpenPGP-1.06&string=key_id_hex&i=1&n=1&C=0 shows that your upack-suggestion is indeed just what is needed:

lib/Crypt/OpenPGP/Certificate.pm
106:sub key_id_hex { uc unpack 'H*', $_[0]->key_id }
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I just didn't recognize the result since I was expecting the short key ID format and that outputs the long format.

The solution is:

print "KeyID hex long: 0x", uc         unpack('H*', $sigobj->key_id)  
+      ,"\n";
print "KeyID hex short: 0x",uc substr( unpack('H*', $sigobj->key_id), 
+-8, 8),"\n";
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