Abstract. In this paper, we investigate the security of the NOEKEON block cipher against side channel cube attacks. NOEKEON was proposed by Daemen et al. for the NESSIE project. The block size and the key size are both 128 bits. The cube attack, introduced by Dinur and Shamir at EUROCRYPT 2009, is a new type of algebraic cryptanalysis. The attack may be applied if the adversary has access to a single bit of information that can be represented by a low degree multivariate polynomial over GF(2) of secret and public variables. In the side channel attack model, the attacker is assumed to have access to some leaked information about the internal state of the cipher as well as the plaintext and ciphertext. Adopting the notion of a single bit leakage as formalized by Dinur and Shamir, we assume that the attacker has only one bit of information about the intermediate state after each round. Using this side channel attack model, we show that it is possible to extract 60 independent linear equations over 99 (out of 128) key variables. To recover the whole 128-bit key, the attack requires only about 2 10 chosen plaintext and O(2 68 ) time complexity.

Abstract. In this paper, we investigate the security of the KATAN family of block ciphers against differential fault attacks. KATAN consists of three variants with 32, 48 and 64-bit block sizes, called KATAN32, KATAN48 and KATAN64, respectively. All three variants have the same key length of 80 bits. We assume a single-bit fault injection model where the adversary is supposed to be able to corrupt a single random bit of the internal state of the cipher and this fault injection process can be repeated (by resetting the cipher); i.e., the faults are transient rather than permanent. First, we determine suitable rounds for effective fault injections by analyzing distributions of low-degree (mainly, linear and quadratic) polynomial equations obtainable using the cube and extended cube attack techniques. Then, we show how to identify the exact position of faulty bits within the internal state by precomputing difference characteristics for each bit position at a given round and comparing these characteristics with ciphertext differences (XOR of faulty and non-faulty ciphertexts) during the online phase of the attack. The complexity of our attack on KATAN32 is 2 59 computations and about 115 fault injections. For KATAN48 and KATAN64, the attack requires 2 55 computations (for both variants), while the required number of fault injections is 211 and 278, respectively.

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Simeck, a lightweight block cipher has been proposed to be one of the encryption that can be employed in the Internet of Things (IoT) applications. Therefore, this paper presents the security of the Simeck32/64 block cipher against side-channel cube attack. We exhibit our attack against Simeck32/64 using the Hamming weight leakage assumption to extract linearly independent equations in key bits. We have been able to find 32 linearly independent equations in 32 key variables by only considering the second bit from the LSB of the Hamming weight leakage of the internal state on the fourth round of the cipher. This enables our attack to improve previous attacks on Simeck32/64 within side-channel attack model with better time and data complexity of 2 35 and 2 11.29 respectively.