Comment Passing Keys (Score 1) 195
When I thought about this problem, if you really want to hide the from/to, you need a third party intermediary. If you want to handle encryption of the subject and message, then a design that leverages P2P would be pretty adequate and acts like a plugin for your favorite mail client.
It operates on a two part design, but it is easier to describe from the recipients point of view. When you receive an encrypted message it comes with a key. When you enter the passphrase for that key, it tells you how to retrieve the actual decryption key from the P2P network. The reason is that the key was broken into randomly sized packets, reordered, and dispersed. That key tells you how to retrieve those pieces and how to reorder them. There should be certain amount of overlap in the packets so that if one or two of the packets are missing, the message can still be recovered (this feature would be selectable option per the key that it came with).
