Paper 2013/756

A Meet-in-the-Middle Attack on Round-Reduced mCrypton Using the Differential Enumeration Technique

Yonglin Hao, Dongxia Bai, and Leibo Li

Abstract

This paper describes a meet-in-the-middle (MITM) attack against the round reduced versions of the block cipher mCrypton-64/96/128. We construct a 4-round distinguisher and lower the memory requirement from $2^{100}$ to $2^{44}$ using the differential enumeration technique. Based on the distinguisher, we launch a MITM attack on 7-round mCrypton-64/96/128 with complexities of $2^{44}$ 64-bit blocks and $2^{57}$ encryptions. Then we extend the basic attack to 8 rounds for mCrypton-128 by adding some key-bridging techniques. The 8-round attack on mCrypton-128 requires a time complexity $2^{100}$ and a memory complexity $2^{44}$. Furthermore, we construct a 5-round distinguisher and propose a MITM attack on 9-round mCrypton-128 with a time complexity of $2^{115}$ encryptions and a memory complexity of $2^{113}$ 64-bit blocks.