Meet-in-the-middle Attack on RAIN-128

RAIN is a lightweight block cipher with SPN structure, which not only has strong security, but also possesses high software and hardware implementation efficiency. Meet-in-the-middle attacks are widely used in the security analysis of block ciphers algorithms. In this paper, the meet-in-the-middle attack on RAIN is researched. By examining the structural characteristics and the properties of truncated differential of RAIN-128, both 4-round and 6-round meet-in-the-middle distinguishers are first constructed by using differential enumeration technique, and meet-in-the-middle attacks on 8-round and 10-round RAIN-128 are presented, respectively. For 8-round attack, in the preprocessing, the time complexity is $ {2^{68}} $ 8-round encryptions, and the memory complexity is $ {2^{75}} $ bit, in the online, the time complexity is $ {2^{109}} $ 8-round encryptions, and the data complexity is $ {2^{72}} $ chosen plaintexts. For 10-round attack, in the preprocessing, the time complexity is $ {2^{214}} $ 10-round encryptions, and the memory complexity is $ {2^{219}} $ bit, in the online, the time complexity is $ {2^{109}} $ 10-round encryptions, and the data complexity is $ {2^{72}} $ chosen plaintexts. The result shows that RAIN-128 can be against meet-in-the-middle attack and has high security redundancy.