Tail-MAC: An Efficient Message Authentication Scheme for Stream Ciphers

A simple and software-efficient algorithm for computing Message Authentication Codes for stream ciphers is described along with the analysis its security. The proposed algorithm was designed to employ some of the data already computed by the underlying stream cipher in the purpose of minimizing the computational cost of the operations required by the MAC algorithm. The performed analyses indicate that the scheme provides a sufficient level of resistance against forgery attacks in a chosen ciphertext attack model, remains simple in its construction and provides high efficiency in software implementations.