PGP has been cracked when you use it with automation in that you can steal keys slowly by relying on the meta-behavior of systems around PGP. A classic attack here is timing how long it takes for a PGP-based automated system to reject your messages.
PGP is intended for the classic "used by a human to encrypt emails manually" flow and is actually insecure if you automate around it.
the timing attack you're describing is extremely common -- not unique to PGP -- and simple to mitigate. do you have more literature about the attack, or attacks, that you're describing?
