Extending Differential Fault Analysis to Dynamic S-Box Advanced Encryption Standard Implementations

Advanced Encryption Standard (AES) is a worldwide cryptographic standard for symmetric key cryptography. Many attacks try to exploit inherent weaknesses in the algorithm or use side channels to reduce entropy. At the same time, researchers strive to enhance AES and mitigate these growing threats. This paper researches the extension of existing Differential Fault Analysis (DFA) attacks, a family of side channel attacks, on standard AES to Dynamic S-box AES research implementations. Theoretical analysis reveals an expected average keyspace reduction of 2-88:9323 after one faulty ciphertext using DFA on the State of Rotational S-box AES-128 implementations. Experimental results revealed an average 2-88:8307 keyspace reduction and confirmed full key recovery is possible

The (related-key) impossible boomerang attack and its application to the AES block cipher

The Advanced Encryption Standard (AES) is a 128-bit block cipher with a user key of 128, 192 or 256 bits, released by NIST in 2001 as the next-generation data encryption standard for use in the USA. It was adopted as an ISO international standard in 2005. Impossible differential cryptanalysis and the boomerang attack are powerful variants of differential cryptanalysis for analysing the security of a block cipher. In this paper, building on the notions of impossible differential cryptanalysis and the boomerang attack, we propose a new cryptanalytic technique, which we call the impossible boomerang attack, and then describe an extension of this attack which applies in a related-key attack scenario. Finally, we apply the impossible boomerang attack to break 6-round AES with 128 key bits and 7-round AES with 192/256 key bits, and using two related keys we apply the related-key impossible boomerang attack to break 8-round AES with 192 key bits and 9-round AES with 256 key bits. In the two-key related-key attack scenario, our results, which were the first to achieve this amount of attacked rounds, match the best currently known results for AES with 192/256 key bits in terms of the numbers of attacked rounds. The (related-key) impossible boomerang attack is a general cryptanalytic technique, and can potentially be used to cryptanalyse other block ciphers

Too Much Crypto

We show that many symmetric cryptography primitives would not be less safe with significantly fewer rounds. To support this claim, we review the cryptanalysis progress in the last 20 years, examine the reasons behind the current number of rounds, and analyze the risk of doing fewer rounds. Advocating a rational and scientific approach to round numbers selection, we propose revised number of rounds for AES, BLAKE2, ChaCha, and SHA-3, which offer more consistent security margins across primitives and make them much faster, without increasing the security risk

MiMC:Efficient Encryption and Cryptographic Hashing with Minimal Multiplicative Complexity

We explore cryptographic primitives with low multiplicative complexity. This is motivated by recent progress in practical applications of secure multi-party computation (MPC), fully homomorphic encryption (FHE), and zero-knowledge proofs (ZK) where primitives from symmetric cryptography are needed and where linear computations are, compared to non-linear operations, essentially ``free\u27\u27. Starting with the cipher design strategy ``LowMC\u27\u27 from Eurocrypt 2015, a number of bit-oriented proposals have been put forward, focusing on applications where the multiplicative depth of the circuit describing the cipher is the most important optimization goal. Surprisingly, albeit many MPC/FHE/ZK-protocols natively support operations in \GF{p} for large $p$, very few primitives, even considering all of symmetric cryptography, natively work in such fields. To that end, our proposal for both block ciphers and cryptographic hash functions is to reconsider and simplify the round function of the Knudsen-Nyberg cipher from 1995. The mapping $F(x) := x^3$ is used as the main component there and is also the main component of our family of proposals called ``MiMC\u27\u27. We study various attack vectors for this construction and give a new attack vector that outperforms others in relevant settings. Due to its very low number of multiplications, the design lends itself well to a large class of new applications, especially when the depth does not matter but the total number of multiplications in the circuit dominates all aspects of the implementation. With a number of rounds which we deem secure based on our security analysis, we report on significant performance improvements in a representative use-case involving SNARKs

Survey and Benchmark of Block Ciphers for Wireless Sensor Networks

Cryptographic algorithms play an important role in the security architecture of wireless sensor networks (WSNs). Choosing the most storage- and energy-efficient block cipher is essential, due to the facts that these networks are meant to operate without human intervention for a long period of time with little energy supply, and that available storage is scarce on these sensor nodes. However, to our knowledge, no systematic work has been done in this area so far.We construct an evaluation framework in which we first identify the candidates of block ciphers suitable for WSNs, based on existing literature and authoritative recommendations. For evaluating and assessing these candidates, we not only consider the security properties but also the storage- and energy-efficiency of the candidates. Finally, based on the evaluation results, we select the most suitable ciphers for WSNs, namely Skipjack, MISTY1, and Rijndael, depending on the combination of available memory and required security (energy efficiency being implicit). In terms of operation mode, we recommend Output Feedback Mode for pairwise links but Cipher Block Chaining for group communications