An Analysis of the Compact XSL Attack on BES and Embedded SMS4

The XSL attack when applied on BES-128 has been shown to have an attack complexity of 2100 , which is faster than exhaustive search. However at FSE 2007, Lim and Khoo analyzed the eprint XSL attack on BES and showed that the attack complexity should be 2401 . Later at IEEE-YCS 2008, Qu and Liu counter-proposed that the compact XSL attack on BES-128 works and has complexity 297 . In this paper, we point out some errors in the attack of Qu and Liu. We also show that the complexity of the compact XSL attack on BES-128 is at least 2209.15 . At Indocrypt 2007, Ji and Hu claimed that the eprint XSL attack on ESMS4 has complexity 277 . By the same method we used to analyze BES, we also show that the complexity of compact XSL attack on ESMS4 is at least 2216.58 . Our analysis adapts the approach of Lim and Khoo to the compact XSL attack, and improves on it by considering the T method that grows the number of equations. Keywords. Compact XSL Attack, BES, ESMS4.

• Type: Conference
• Year: 2009
• Where: CANS
• Authors: Jiali Choy, Huihui Yap, Khoongming Khoo
• Keywords: Attack Complexity, CANS 2009, Cryptology, Eprint Xsl Attack, Xsl Attack