On Linear Cryptanalysis of MBAL Ciphers

摘要

This paper studies the linear cryptanalysis of the MBAL (MultiBlock Algorithm) Cipher. MBAL includes SXAL8 Cipher and 3-round Fm funtion. Moreover, the Size of the input data is variable. In this paper, we propose The strategy of making linear approximations for MBAL Which are independent of SXAL8 and the size of the input Dat. We succeed in making an approximation with bias 2~-5.49 from the first to second (or second to third) rounds, where the bias is defined as |Prob-1/2|.