chapter  5
36 Pages

Authentication Codes

One of the main goals of a cryptographic system is to provide authentication, which simply means providing assurance about the content and origin of the communicated message. Traditionally, it was assumed that a secrecy system provides authentication by virtue of the secret key being only known to the intended communicants; this would prevent an enemy from constructing a fraudulent message. Simmons in [145] argued that the two goals of cryptography are independent. He showed that a system that provides perfect secrecy might not provide any protection against authentication threats. Similarly, a system can provide perfect authentication without concealing the message.