Improved Differential-Linear Cryptanalysis of Reduced-Round SAFER＋＋

摘要

In this paper we present differential-linear cryptanalysis of SAFER++ reduced to 4 and 5 rounds. For 4 rounds, we can find 51 key bits of 128-bit master keys,and 67 key bits of 256-bit master keys using 238 chosen plaintexts. For 5 rounds, we can find 58 key bits of 128-bit master keys, and 82 key bits of 256-bit master keys using 246 chosen plaintexts. All attacks are applicable to a fraction of 2-6 of the corresponding key space. For 256-bit master keys, the attack complexity are reduced greatly compared with those using linear cryptanalysis for 4-round by Jorge Nakahara and the differential-nonlinear cryptanalysis for 4-round by us.