International Association for Cryptologic Research (IACR)
Abstract
The Simeck family of lightweight block ciphers was proposed in CHES 2015 which combines the good design components from NSA designed ciphers SIMON and SPECK. Dynamic key-guessing techniques were proposed by Wang {\it et al.} to greatly reduce the key space guessed in differential cryptanalysis and work well on SIMON. In this paper, we implement the dynamic key-guessing techniques in a program to automatically give out the data in dynamic key-guessing procedure and thus simplify the security evaluation of SIMON and Simeck like block ciphers regarding differential attacks. We use the differentials from Kölbl {\it et al.}\u27s work and also a differential with lower Hamming weight we find using Mixed Integer Linear Programming method to attack 22-round Simeck32, 28-round Simeck48 and 35-round Simeck64. Besides, we launch the same attack procedure on four members of SIMON family by use of newly proposed differentials in CRYPTO2015 and get new attack results on 22-round SIMON32/64, 24-round SIMON48/96, 28, 29-round SIMON64/96 and 29, 30-round SIMON64/128. As far as we are concerned, our results on SIMON64 are currently the best results
