Introduction- Telephone

When you have an untappable wire between the sender and recipient, then traffic analysis is impossible (and crypto unnecessary). Yet you can create an untappable wire with cryptography! The device in question is called a link encryptor. Take a stream cipher and run it continuously across the channel in question. Pad the asynchronous traffic when it's not flowing and add some synchronization to both the stream and the data insertion. You can tap the physical line still, but the interceptions reveal zero information (computationally--the stream cipher _is_ keyed, after all). A good project would be virtual link encryptors for the Internet. Eric