[Cryptography] Cryptographic challenge

[jamesd at echeque.com]

This challenge seems rather pointless, because for forward secrecy, 
always want ephemeral keys, and ephemeral keys always provide the 
possibility of a hidden channel.

Hidden channels are a weak security threat, because if we don't trust 
one of the participants, we are hosed regardless.  The point of 
cryptography is to keep insider information inside.  If you have an 
entryist, you are toast.