Distinguishing Attack on a Modified Version of MAG Stream Cipher

MAG is a synchronous stream cipher designed by Vuckovac submitted to the eSTREAM project.Vuckovac also proposed two modified versions of MAG to avoid the distinguishing attack on the first version of MAG presented by Fischer. In this paper we show that, changing the Fischer’s attack we can apply it to one of the modified versions of MAG. The modified attack requires only 514 successive bytes of known keystream and 5 xor and 2 comparison operations between 16 bit words. In addition, we show that distinguishing and key recovery attack proposed by Simpson and Henricksen on all versions of MAG is feasible just by considering an assumption on initialization of MAG that simplifies this step so much. Therefore, their attack cannot be performed in general.

Keywords:

Cryptanalysis , MAG Stream Cipher , Distinguishing Attack , Estream