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XSL block ciphers are based on Shannon's principles of confusion and diffusion. Round functions of these ciphers consist of round key addition, a substitution and a linear transformation. In this paper, the combinatorial properties of the group generated by the linear transformation and all round keys XORaddition are described.

The paper presents a fault attack on reconfigurable FSMbased cipher of Zakrevskij. The faulty effect is assumed to be transient. The attack is based on the single stuck-at fault model and a solution of the problem of finite-state machine identification. Simple conditional experiments with automata are used.

The paper proposes a scheme for constructing one-way function in a group with decidable word problem and undecidable endomorphism problem, and a corresponding authentication protocol. Possible prerequisites for reliability of the proposed scheme are analysed.

In this paper key-scheduling algorithms having the defined recurrent property are considered. For this class of algorithms we describe related-key attacks. The complexity of the attack is equal to the exhaustive search of one round key. It requires a little number of plaintexts.

In this paper we describe a differential attack on a block cipher in a general case. We calculate the attack complexity for different cipher parameters.

The paper considers the peculiarities of authentication in multi-tier environment and corresponding security problems. The authentication protocol for multi-tier system based on commutative encryption is provided.

In the paper, we provide the analysis of perturbed quantization steganography applied to JPEG images. The ability of determining so-called changeable coefficients is discussed and an approach for that is proposed. This approach allows to create stegosystem that would take advantage of properties of perturbed quantization steganography but would use images in JPEG format as cover images.