cdodhner@indirect.com (Christian D. Odhner) says:

I could very well be wrong about this one, but since pgp uses a random idea session key each time you encrypt, wouldn't that in fact ensure that no two encryptions of the same file with the same public key are ever the same? Why then would random stuff be needed?

I knew that! I forgot that! Thanks for reminding me. Back to the drawing board! A protocol where the user controlled the session key would be more awkward but would solve that problem. On the otherhand that isn't the PGP protocol.