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Security and Communication Networks
Volume 2017 (2017), Article ID 1461520, 10 pages
https://doi.org/10.1155/2017/1461520
Research Article

New Linear Cryptanalysis of Chinese Commercial Block Cipher Standard SM4

1Key Laboratory of Cryptologic Technology and Information Security, Ministry of Education, Shandong University, Jinan, China
2Weifang University, Weifang, China

Correspondence should be addressed to Meiqin Wang; nc.ude.uds@gnawqm

Received 8 June 2017; Accepted 1 August 2017; Published 6 September 2017

Academic Editor: Jesús Díaz-Verdejo

Copyright © 2017 Yu Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

SM4 is a Chinese commercial block cipher standard used for wireless communication in China. In this paper, we use the partial linear approximation table of S-box to search for three rounds of iterative linear approximations of SM4, based on which the linear approximation for 20-round SM4 has been constructed. However, the best previous identified linear approximation only covers 19 rounds. At the same time, a linear approximation for 19-round SM4 is obtained, which is better than the known results. Furthermore, we show the key recovery attack on 24-round SM4 which is the best attack according to the number of rounds.