An experiment on DES statistical cryptanalysis

Linear cryptanalysis and differential cryptanalysis are the most important methods of attack against block ciphers. Their efficiency have been demonstrated against several ciphers, including the Data Encryption Standard. We prove that both of them can be considered, improved and joined in a more general statistical framework. We also show that the very same results as those obtained in the case of DES can be found without any linear analysis and we slightly improve them into an attack with theoretical complexity 242.9 We can apply another statistical attack-the ?2 cryptanalysis-on the same characteristics without a definite idea of what happens in the encryption process. It appears to be roughly as efficient as both differential and linear cryptanalysis. We propose a new heuristic method to find good characteristics. It has found an attack against DES absolutely equivalent to M. Matsui's (1994) one by following a distinct path.

Cryptanalysis of the full MMB Block Cipher

Jorge Nakahara, Yue Sun

The block cipher MMB was designed by Daemen, Govaerts and Vandewalle, in 1993, as an alternative to the IDEA block cipher. We exploit and describe unusual properties of the modular multiplication in ZZ232 −1 , which lead to a diﬀerential attack on the full 6-round MMB cipher (both versions 1.0 and 2.0). Further contributions of this paper include detailed square and linear cryptanalysis of MMB. Concerning diﬀerential cryptanalysis (DC), we can break the full MMB with 2118 chosen plaintexts, 295.91 6-round MMB encryptions and 264 counters, eﬀectively bypassing the cipher’s countermeasures against DC. For the square attack, we can recover the 128-bit user key for 4-round MMB with 234 chosen plaintexts, 2126.32 4-round encryptions and 264 mem- ory blocks. Concerning linear cryptanalysis, we present a key-recovery attack on 3-round MMB requiring 2114.56 known-plaintexts and 2126 en- cryptions. Moreover, we detail a ciphertext-only attack on 2-round MMB using 293.6 ciphertexts and 293.6 parity computations. These attacks do not depend on weak-key or weak-subkey assumptions, and are thus in- dependent of the key schedule algorithm.

Springer2009

Cryptanalysis of the full MMB block cipher

Jorge Nakahara, Yue Sun

The block cipher MMB was designed by Daemen, Govaerts and Vandewalle, in 1993, as an alternative to the IDEA block cipher. We exploit and describe unusual properties of the modular multiplication in

Z_{2^{32} - 1}

, which lead to a differential attack on the full 6-round MMB cipher (both versions 1.0 and 2.0). Further contributions of this paper include detailed square and linear cryptanalysis of MMB. Concerning differential cryptanalysis (DC), we can break the full MMB with 2^118 chosen plaintexts, 2^95.91 6-round MMB encryptions and 2^64 counters, effectively bypassing the cipher's countermeasures against DC. For the square attack, we can recover the 128-bit user key for 4-round MMB with 2^34 chosen plaintexts, 2^126.32 4-round encryptions and 2^64 memory blocks. Concerning linear cryptanalysis, we present a key-recovery attack on 3-round MMB requiring 2^114.56 known-plaintexts and 2^126 encryptions. Moreover, we detail a ciphertext-only attack on 2-round MMB using 2^93.6 ciphertexts and 2^93.6 parity computations. These attacks do not depend on weak-key or weak-subkey assumptions, and are thus independent of the key schedule algorithm.

2009

DES S-box generator

Lauren De Meyer, Serge Vaudenay

The Data Encryption Standard (DES) is a cryptographic algorithm, designed by IBM, that was selected to be the national standard in 1977 by the National Bureau of Standards. The algorithm itself was entirely published but the design criteria were kept secret until 1994 when Coppersmith, one of the designers of DES, published them. He states that the IBM team already knew about the attack called Differential cryptanalysis during the design of the algorithm and that it had an effect on choosing the S-boxes. To be more specific, he mentions eight design criteria that all the S-boxes of DES are based on. How the S-boxes were generated is a mystery, as the legend says this was outsourced to the NSA. Indeed, building a set of S-boxes respecting these criteria is a non-trivial task. In this paper we present an efficient S-box generator respecting all criteria and even more. Coppersmith's design criteria served as a basis but were strengthened for better resistance to Linear Cryptanalysis. While other researchers have already proposed S-box generators for DES satisfying either non-linearity or good diffusion, our generator offers both. Moreover, apart from suggesting a new set of 8 S-boxes, it can also very quickly produce a large pool of S-boxes to be used in further research.

Taylor & Francis Inc2016

Cryptanalysis of the full MMB block cipher

Jorge Nakahara, Yue Sun

The block cipher MMB was designed by Daemen, Govaerts and Vandewalle, in 1993, as an alternative to the IDEA block cipher. We exploit and describe unusual properties of the modular multiplication in

Z_{2^{32} - 1}

2009