How to expose an eavesdropper

We present a new protocol for establishing secure communications over an insecure communications charmel in the absence of trusted third parties or authenticated keys. The protocol is an improvement over the simpler protocol in which the communicating parties exchanged their public encryption keys and used them to encrypt messages. It forces a potential eavesdropper--if he wants to understand the messages--to reveal his existence by modifying and seriously garbling the communication.