Cryptology ePrint Archive: Report 2013/626

Improved Linear Attacks on the Chinese Block Cipher Standard

Mingjie Liu and Jiazhe Chen

Abstract: The block cipher used in the Chinese Wireless LAN Standard (WAPI), SMS4, was recently renamed as SM4, and became the block cipher standard issued by the Chinese government. This paper improves the previous linear cryptanalysis of SMS4 by giving the first 19-round one-dimensional approximations. The 19-round approximations hold with bias 2^{−62.27}; we use one of them to leverage a linear attack on 23-round SMS4. Our attack improves the previous 23-round attacks by reducing the time complexity. Furthermore, the data complexity of our attack is further improved by the multidimensional linear approach.

Category / Keywords: secret-key cryptography / Block Cipher, SMS4, Linear Cryptanalysis, Multidimensional Linear Cryptanalysis

Date: received 29 Sep 2013, last revised 1 Oct 2013

Contact author: liumj9705 at gmail com

Available format(s): PDF | BibTeX Citation

Note: Acknowledgments updated

Version: 20131001:140746 (All versions of this report)

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