Abstract—Halka is a lightweight block cipher proposed by Sourav Das in 2014. The block length of Halka is 64 bits and its key length is 80 bits. Halka uses 8-bit S-box for nonlinear permutation and uses bit shuffle for the linear permutation. In the differential cryptanalysis by the designers, the number of active S-box at each round is estimated to be 2, and differential attack can be mounted up to 5 rounds of Halka. In this article, focusing on Halka that has bit shuffle and 1-bit difference of active S-box at each round, we derive the new maximum differential characteristic probability (DCP). By analyzing trellis diagram of differential trails, we newly find that the maximum DCP of Halka is 2
60 for 10 rounds of single trail and 2
62.58 for 13 rounds of multiple trail, which are the results that the designers would not report.
Index Terms—Differential cryptanalysis, block cipher Halka, multiple trail, 1-bit difference.
Y. Igarashi and T. Kaneko are with the Department of Electrical Engineering, Tokyo University of Science, Noda, Chiba, 2788510 Japan (e-mail: yasutaka@rs.noda.tus.ac.jp).
S. Nakazawa was with the Department of electrical engineering, Tokyo University of Science, Noda, Chiba, 2788510 Japan.
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Cite: Yasutaka Igarashi, Shun Nakazawa, and Toshinobu Kaneko, "Differential Cryptanalysis of Block Cipher Halka," International Journal of Information and Electronics Engineering vol. 10, no. 2, pp. 40-43, 2020.
