Problems with compatibility between GnuPG 1.2.2 and PGPTools 7.0.3

[David Shaw]

On Thu, Sep 04, 2003 at 06:06:41PM +0200, Boix Ricart Marc wrote:
> Hello all,
> 
> I'm trying to validate keys compatibility between the GnuPG v1.2.2 for 
> Microsoft Windows and the soft PGPTools ver 7.0.3.
> With public keys I didn't found any problem, but if I try to import secret 
> keys  errors appears...
> 
> First, when:
>         - I import a RSA legacy pair of keys (generated with PGPTools) in 
> GnuPG,
>         - Next I encrypt a message with the public key (of the previous 
> pair) with PGPTools
>         - And finally I try to decrypt the message with GnuPG
> I receive the error GPGME_Cipher_IDEA (I'm using GPGMe to develop). Do you 
> know if it's normal?

Yes.  PGP assumes that if you are encrypting to a legacy RSA key (aka
"v3 RSA"), then it must use IDEA as the cipher.  GnuPG doesn't have
IDEA by default (see http://www.gnupg.org/why-not-idea.html), so this
doesn't work.

The answer is not to use legacy RSA keys.  Use regular modern RSA
keys.

> And now, my big problem!
>         - I generate a pair of keys (the type isn't important) with GnuPG
>         - I export the secret key from GnuPG and I import it in PGPTools.
>         - Next I encrypt a message with its public key with GnuPG.
>         - And finally I try to decrypt the message with PGPTools
> The PGPTools not recognize the passphrase of the secret key. Actually, 
> PGPTools has correctly imported the secret key, but it doesn't catch the 
> passphrase, because if I try to sign with the same secret key with 
> PGPTools, it say that the secret key hasn't passphrase.
> I don't understand why! ;P

GnuPG uses a more secure way to store secret keys, but PGP 7 can't
handle it (PGP 8 can).  Do this:

gpg --simple-sk-checksum --edit (thekey)
passwd
(Change the password.  You can change it back to the same thing if you
like.)
save

Now you have a secret key that PGP 7 can handle.

David