In this paper, we present an improved differential-linear cryptanalysis of the ChaCha stream cipher. Our main contributions are new distinguishers that were able to build thanks following improvements: a) considered a larger search space, including 2-bit differences (besides 1-bit differences) for difference at beginning differential part trail; b) better choice mask between and linear parts; c...

In this paper, we consider the statistical decision processes behind a linear and a differential cryptanalysis. By applying techniques and concepts of statistical hypothesis testing, we describe precisely the shape of optimal linear and differential distinguishers and we improve known results of Vaudenay concerning their asymptotic behaviour. Furthermore, we formalize the concept of “sequential...

QARMA is a recently published lightweight tweakable block cipher, which has been used by the ARMv8 architecture to support a software protection feature. In this paper, using the method of MITM, we give the first distinguisher of QARMA block cipher. It is made up of the Pseudo-Reflector construction with two forward rounds and three backward rounds. By adding two rounds on the top and three rou...

Baldi et al. proposed a variant of McEliece’s cryptosystem. The main idea is to replace its permutation matrix by adding to it a rank 1 matrix. The motivation for this change is twofold: it would allow the use of codes that were shown to be insecure in the original McEliece’s cryptosystem, and it would reduce the key size while keeping the same security against generic decoding attacks. The aut...

Encryption algorithms will transform a human interpretable text block or information in to a non-interpretable block of symbols. The objective of any such encryption algorithm will be making the cipher block more non-interpretable and seemingly random block of symbols. So any cipher block will always be random and will purely be a set of random permutations of symbols. The efforts of distinguis...

This paper develops several new techniques of cryptanalyzing MACs based on block ciphers, and is divided into two parts. The first part presents new distinguishers of the MAC construction Alred and its specific instance Alpha-MAC based on AES. For the Alred construction, we first describe a general distinguishing attack which leads to a forgery attack directly with the complexity of the birthda...

Evaluating side-channel attacks and countermeasures requires determining the amount of information leaked by a target device. For this purpose, information extraction procedures published so far essentially combine a “leakage model” with a “distinguisher”. Fair evaluations ideally require exploiting a perfect leakage model (i.e. exactly corresponding to the true leakage distribution) with a Bay...

SHACAL is a 160-bit block cipher based on the hash standard SHA-1, as a submission to NESSIE. SHACAL uses the XOR, modular addition operation and the functions of bit-by-bit manner. These operations and functions make the differential cryptanalysis difficult, i.e, it is hard to find a long differential characteristic with high probability. But, we can find short differential characteristics wit...

The hash function Skein is the submission of Ferguson et al. to the NIST Hash Competition, and is arguably a serious candidate for selection as SHA-3. This paper presents the first third-party analysis of Skein, with an extensive study of its main component: the block cipher Threefish. We notably investigate near collisions, distinguishers, impossible differentials, key recovery using related-k...

We present two practical attacks on the CAESAR candidate PAES. The rst attack is a universal forgery for any plaintext with at least 240 bytes. It works for the nonce-repeating variant of PAES and in a nutshell it is a state recovery based on solving di erential equations for the S-Box leaked through the ciphertext that arise when the plaintext has a certain di erence. We show that to produce t...