New Truncated Differential Cryptanalysis on 3D Block Cipher

Abstract

This paper presents 11- and 13-round key-recovery attacks on block cipher 3D with the truncated differential cryptanalysis, while the previous best key-recovery attack broke only 10 rounds with the impossible differential attack. 3D is an AES-based block cipher proposed at CANS 2008, which operates on 512-bit blocks and a 512-bit key, and consists of 22 rounds. It was previously believed that the truncated differential cryptanalysis could not extend the attack more than 5 rounds. However, by carefully analyzing the data processing part and key schedule function simultaneously, we show the attack to 11-round 3D with 2251 chosen plaintext (CP), 2288 computations, and 2128 memory. Additionally, the time complexity is improved up to 2113 by applying the early aborting technique. By utilizing the idea of neutral bit, we attack 13-round 3D with 2469 CP, 2308 computations, and 2128 memory.