Related-key rectangle cryptanalysis of Rijndael-160 and Rijndael-192

Abstract

In this study, the authors present the first related-key rectangle cryptanalysis of Rijndael-160/160 and Rijndael-192/192. The author's attack on Rijndael-160/160 covers eight rounds. The attack complexities are 2126.5 chosen plaintexts, 2129.28 8-round Rijndael-160/160 encryptions and 2132.82 bytes. Their attack on Rijndael-192/192 covers ten rounds. It requires 2179 chosen plaintexts, 2181.09 10-round Rijndael-192/192 encryptions and 2185.59 bytes memory. These are the currently best cryptanalytic results on Rijndael-160/160 and Rijndael-192/192 in terms of the number of attacked rounds. Furthermore, their results show that the slow diffusion in the key schedule of Rijndael makes it a target for this type of analysis.