Security in Computing, Third Edition

10.3. Public Key Encryption Systems

In 1976, Diffie and Hellman [DIF76] proposed a new kind of system, public key encryption, in which each user would have a key that did not have to be kept secret. Counterintuitively, the public nature of the key would not inhibit the system's secrecy. The public key transformation is essentially a one-way encryption with a secret (private) way to decrypt.

Public key systems have an enormous advantage over conventional key systems: Anyone can send a secret message to a user, while the message remains adequately protected from being read by an interceptor. With a conventional key system, a separate key is needed for each pair of users. As we have seen, n users will require n * (n – 1)/2 keys. As the number of ...