Cryptanalysis of the XO-64 Suitable for Wireless Systems

Data-dependent operations (DDOs) that were introduced by Moldovyan in 2003 (Moldovyan in MMM-ACNS 2003, LNCS, 2776: 316–327, Springer, Heidelberg, 5; Moldovyan et al. in Int J Netw Secur 2(2):114–225, 6, in Proceedings of CCCT04, VII:123–128, 7), have been proposed as a primitive suitable for designing efficient ciphers with simple key scheduling. DDOs solve problems arising due to the weaknesses in key change process, and also the DDO-based ciphers provide a better performance with smaller hardware requirement for implementation. Along with Eagle-64 (Moldovyan et al. 7), Eagle-128 (Moldovyan et al. 6), MD-64 (Minh et al. in Int J Comput Sci Netw Secur 10(3):54–60, 15), KT-64 (Minh et al. in IJCSNS 19(1):10–18, 13) … block ciphers are being designed, XO-64 (Minh et al. in Advanced Technologies for Communications, ATC, 409–412, 1) is a block cipher of this type which is better in terms of applicability, flexibility in fast and efficient wireless system, as well as security against known attack methods, such as slide attack and differential attack. In this paper, by applying a way of related-key attacks, we present the possibility to break the XO-64 cipher with high probability. We propose a related-key amplified boomerang attack using the differential characteristics on a 7-round reduced XO-64, requiring complexities of 244 in data, 247 bytes in memory, and 265 in computational time. This study can be considered as the first cryptographic result on XO-64.