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Abstract. Using a new 4-round impossible differential in AES that allows us to exploit the redundancy in the key schedule of AES-128 in a way more effective than previous work, we present a new impossible differential attack on 7 rounds of this block cipher. By this attack, 7-round AES-128 is breakable with a data complexity of about 2 106 chosen plaintexts and a time complexity equivalent to about 2 110 encryptions. This result is better than any previously known attack on AES-128 in the single-key scenario.

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Abstract. Many modern block ciphers use maximum distance separable (MDS) matrices as the main part of their diffusion layers. In this paper, we propose a new class of diffusion layers constructed from several rounds of Feistel-like structures whose round functions are linear. We investigate the requirements of the underlying linear functions to achieve the maximal branch number for the proposed 4 × 4 words diffusion layer. The proposed diffusion layers only require word-level XORs, rotations, and they have simple inverses. They can be replaced in the diffusion layer of the block ciphers MMB and Hierocrypt to increase their security and performance, respectively. Finally, we try to extend our results for up to 8 × 8 words diffusion layers.

Due to their remarkable application in many branches of applied mathematics such as combinatorics, coding theory, and cryptography, Vandermonde matrices have received a great amount of attention. Maximum distance separable (MDS) codes introduce MDS matrices which not only have applications in coding theory but also are of great importance in the design of block ciphers. Lacan and Fimes introduce a method for the construction of an MDS matrix from two Vandermonde matrices in the finite field. In this paper, we first suggest a method that makes an involutory MDS matrix from the Vandermonde matrices. Then we propose another method for the construction of 2 n × 2 n Hadamard MDS matrices in the finite field G F(2 q ). In addition to introducing this method, we present a direct method for the inversion of a special class of 2 n × 2 n Vandermonde matrices.Keywords MDS matrix · Vandermonde matrix · Hadamard matrix · Blockcipher Mathematics Subject Classification (2000) 11T71 · 14G50 · 51E22 · 94B05 · 20H30 · 15A09 Communicated by J. Jedwab. M. Sajadieh (B) · M. Dakhilalian

SUMMARY mCrypton is a 64‐bit lightweight block cipher designed for use in low‐cost and resource‐constrained applications such as RFID tags and sensors in wireless sensor networks. In this paper, we investigate the strength of this cipher against related‐key impossible differential cryptanalysis. First, we construct two 6‐round related‐key impossible differentials for mCrypton‐96 and mCrypton‐128. Then, using these distinguishers, we present 9‐round related‐key impossible differential attacks on these two versions. The attack on mCrypton‐96 requires 259.9 chosen plaintexts, and has a time complexity of about 274.9 encryptions. The data and time complexities for the attack on mCrypton‐128 are 259.7 chosen plaintexts and 266.7 encryptions, respectively. Copyright © 2011 John Wiley & Sons, Ltd.

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Abstract. Camellia, a 128-bit block cipher which has been accepted by ISO/IEC as an international standard, is increasingly being used in many cryptographic applications. In this paper, using the redundancy in the key schedule and accelerating the filtration of wrong pairs, we present a new impossible differential attack to reduced-round Camellia. By this attack 12-round Camellia-128 without F L/F L −1 functions and whitening is breakable with a total complexity of about 2 116.6 encryptions and 2 116.3 chosen plaintexts. In terms of the numbers of the attacked rounds, our attack is better than any previously known attack on Camellia-128.