Message authentication, an applications of cryptography, has been developed for the protection of files in computer systems from forgery and accidental modifications. Most message authentication methods are based on the computation of an authenticated value by compressing the message using authentication function.
However, messages authenticated based on Data Encryption Standard (DES) algorithm or Modulo-N operation can be forged by various attacks like forward attack, backward attack or birthday attack. For example, DES cryptographic key or the modulo value is independent of message content, hackers can forge messages by forward attack. And also if the authentication function is invertible, hackers can produce messages with matching authenticated value using backward attack or birthday attack.
In this thesis, an authentication function using variable modulo value is proposed to avoid the problems of previous schemes. It is shown that this proposed authentication function is strong against the previous attack. Finally, a possible application of this authentication function to detect computer viruses is discussed.
