Paper 2021/674

On the Effect of the Key-expansion Algorithm in Simon-like Ciphers

Jinyu Lu and Yunwen Liu and Tomer Ashur and and Chao Li

Abstract

In this work we investigate how the choice of the key-expansion algorithm and its interaction with the round function affect the resistance of Simon-like ciphers against rotational-XOR (RX) cryptanalysis. We observe that among the key-expansion algorithms we consider, Simon is most resistant, while Simeck is much less so. Implications on lightweight ciphers design are discussed and open questions are proposed.