Secure Communications in the Presence of Pervasive Deceit

The functions of secrecy, identification of the transmitter and of authentication of messages, and combinations of these, are in principle all achievable using either symmetric or asymmetric cryptosystems. Since secure communications depend on authenticated data exchanges between and/or authenticated actions by some of the parties to the communication, the fundamentals of authentication using symmetric or asymmetric techniques are developed. The surprising conclusion is that they differ only in the secure exchanges required to achieve further secure communications. The problem of authenticating a public-key directory is discussed in the light of these findings.