Modern security tools can largely resist standard attack vectors, but they do not protect against little-known attacks, which may not be protected against. The solution to this problem can be the introduction of hidden traps into the complex to protect against attacks. This technology is a tool that can be configured to solve a wide range of information security problems in an enterprise. A honeypot can complement the existing security system of an enterprise and be a means of collecting important information for the security system. The paper discusses the algorithms for the operation of such systems, and also proposes a system for collecting and processing information from various honeypots, methods of tuning and testing.

The possibility of training neural networks to decrypt encrypted messages using plaintext-ciphertext pairs with an unknown secret key is investigated. An experimental simple 8-bit substitution-permutation cipher is considered. The neural network is a three-layer perceptron with forward propagation. The required volume of the training sample, the probability of an error after training, and the dependence of these parameters on the number of rounds of the encryption transformation are analyzed. One of the main results is conclusion that the considered model did not show an explicit dependence of the complexity of cryptanalysis using neural networks on the number of rounds in the encryption transformation. Thus the question of the optimality of the chosen neural networks architecture for the selected cipher remained open.

The adaptation and application of the method for estimating the upper bound of the probability of two­round differentials for the block symmetric cipher Kalyna is carried out. This cipher was adopted as the Ukrainian standard DSTU 7624: 2014 in 2015. Known methods allow getting only the approximate value of this parameter for this cipher or cannot be applied explicitly through the structural features of this cipher. Using the approximate probability of two­round differentials gives an even greater error in the evaluation of the probabilities of differentials with a large number of rounds, as well as in assessing the resistance of the encryption algorithm to other types of differential attacks. The main stages of the used method are the following: definition of the minimum number of active S­boxes; definition of the type of differential characteristic having the maximum probability; determination of the number and probabilities of additional differential characteristics. In the course of research, an adapted method has allowed clarifying the upper bound of the probability of 2­round differentials for the cipher Kalyna significantly. This bound is ≈2–47.3 instead of 2–40 when using the method for nested SPN ciphers. The elaborated upper bound of the probability of 2­round differentials allowed clarifying also the bound value of the probability of 4­round differentials. For Kalyna­128 (block size 128 bits), the value is specified 214.6 times, for Kalyna­256 – 229.2 times, Kalyna­512 – 258.4 times. The main advantage of the method adapted for the Kalyna cipher was the possibility of a significant specification of the upper bound of the probability of a 2­round differential. The disadvantage of the adapted method is that assumptions are made, such as, for example, the use of one substitution instead of four in the original algorithm. The result of this assumption is that a real bound of the probability of 2­round differentials could be even smaller.

The Transport Layer Security (TLS) is cryptographic protocol that provides confidentiality and integrity of data in untrusted networks connections. The protocol is composed of two layers: the TLS Record Protocol for encapsulation of various higher-level protocols and the TLS Handshake Protocol for connection security. Nowadays TLS has become the secure standard of choice for Internet and mobile applications. There are many attacks on the TLS protocol that exploit its vulnerabilities: Cipher Block Chaining (CBC) mode encryption, data compression, using obsolete cypher suites and hash functions. Therefore, it is necessary to identify and examine existing threats of TLS. The paper explores the TLS protocol versions and main differences between them. In addition we consider the brand-new TLS version — TLS 1.3. Well-known network attacks (BEAST, CRIME, BREACH and DROWN), several additional attacks (SLOTH, ROBOT, Lucky 13) and their features are also considered. Finally, we compare reviewed attacks using own criteria that will help to understand the security of the TLS protocol at that moment.

An approach for estimating the security of Grostl-like hashing algorithms to collision rebound attacks is proposed. The Kupyna algorithm, adopted as the new Ukrainian standard of hashing, belongs to this kind of hash functions. The proposed approach is based on determining the boundary number of rounds for each stage of the transformation of the difference (fragment of the byte differential characteristic). The boundary number of rounds for the inbound part of the byte differential characteristic is determined based on an analysis of the results from known works. The boundary number of rounds for outbound parts of the byte differential characteristic is determined based on the known probability constraints for Rijndael-like ciphers. The proposed approach is applied to the Kupyna algorithm, adopted as the national Ukrainian standard DSTU 7564: 2014. It is shown that the presence of 5 or more rounds in each of the P and Q transformations of this hashing algorithm makes it resistant to rebound attacks

Trends in the development of symmetric cryptography are constantly associated with the increasing of the sizes of keys and blocks. Block ciphers, which are used today in hashing algorithms, usually have a block size of 512 or 1024 bits. One of the main requirements for symmetric crypto algorithms is to provide resistance to known cryptanalytical attacks. Known methods of security estimation against impossible differential attack have too high complexity for such block sizes. The proposed approach for proving the absence of impossible differentials is applicable to some types of block ciphers and allows proving theoretically the resistance to impossible differentials attack. Rijndael-like SPN ciphers and Feistel ciphers are analyzed. For the group of Rijndael-like ciphers, the absence of byte impossible differentials for 4 or more rounds is proved. For the group of Feistel ciphers, the absence of byte impossible differentials for 6 or more rounds is proved. The first statement made it possible to prove the absence of byte impossible differentials for 4 or more rounds of the cipher Kalyna (DSTU 7624: 2014) with all block sizes, for 512-bit block ciphers that are used in the hash functions Whirlpool, Groestl and Kupyna (DSTU 7564: 2014). The second statement was used to prove the absence of byte impossible differentials for 6 or more rounds of Tornado and Labyrinth ciphers with a block size of 128 bits. Computational experiments on the impossible differentials search for these reduced models confirmed the validity of the obtained theoretical conclusions

On the 1st of July, 2015 Ukraine adopts new cryptographicstandard of symmetric block transformation DSTU7624:2014 which defines “Kalyna” cipher and its confidentialityand integrity modes of operation. The nationalstandard is developed as collaboration result of State Serviceof Special Communication of Ukraine and leadingUkrainian scientists based on the public cryptographicalgorithms competition. In comparison to well-knownstandard AES, DSTU 7624:2014 provides higher level ofcryptographic strength (with possibility of application ofblock and key length up to 512 bits) and comparable orhigher performance on modern software or softwarehardwareplatforms, essentially exceeding rates of DSTUGOST 28147:2009 (GOST 28147-89) which have beenused over 25 years. It is considered modern problems ofblock cipher development and their solutions implementedby the developers in the new national standard of Ukraine.

The Kalyna block cipher was selected during Ukrainian National Public Cryptographic Competition (2007-2010) and its slight modification was approved as the new encryption standard of Ukraine in 2015. Main requirements for Kalyna were both high security level and high performance of software implementation on general-purpose 64-bit CPUs. The cipher has SPN-based (Rijndael-like) structure with increased MDS matrix size, a new set of four different S-boxes, preand postwhitening using modulo 264 addition and a new construction of the key schedule. Kalyna supports block size and key length of 128, 256 and 512 bits (key length can be either equal or double of the block size). At the time of this paper publishing, no more effective cryptanalytic attacks than exhaustive search are known. In this paper we present the adapted English translated specification of Kalyna as it is given in the national standard of Ukraine.

The Kupyna hash function was approved as the new Ukrainian standard DSTU 7564:2014 in 2015. Main requirements for it were both high security level and good performance of software implementation on general-purpose 64-bit CPUs. The new hash function uses DaviesMeyer compression function based on Even-Mansour cipher construction. Kupyna is built on the transformations of the Kalyna block cipher (Ukrainian standard DSTU 7624:2014 [1, 2]). In this paper we present the adapted English translated specification of the Kupyna hash function as it is described in the national standard of Ukraine.

The modified method of estimation of the resistance of block ciphers to truncated byte differential attack is proposed. The previously known method estimate the truncated byte differential probability for Rijndael-like ciphers. In this paper we spread the sphere of application of that method on wider class of ciphers. The proposed method based on searching the most probable truncated byte differential characteristics and verification of sufficient conditions of effective byte differentials absence.

ABSTRACT The strength of Rijndael-like ciphers to the truncated differential attack is considered. Theorems about the absence of effective truncated (byte) differential characteristics and effective truncated (byte) differentials for ciphers with sufficient number of rounds are proved.

The extension of the known method of estimation of the minimal number of active S-boxes in the differential or linear characteristic of Rijndael-like symmetric block ciphers is proposed. Variant of Rijndael cipher with modified linear transformation which provides better diffusion is offered.

Five symmetric block ciphers were proposed to Ukrainian national public cryptographic competition. Developers used different methods for achieving security and performance of the algorithms. An overview of proposed symmetric block ciphers and results of their security analysis is given in this paper.

The analysis of existing requirements for MDS matrices that are used in block ciphers is performed, the most important requirements are selected, and matrix corresponding to the selected requirements is constructed.

The existing methods of performing the estimation of the byteoriented ciphers resistance to truncated differentials attack are considered. The approach allowing to estimate resistance of the feistel ciphers with rijndael-like round transformation and the large size of the block (more then 128 bits) to attack of truncated differentials is proved.

The main attention is given to study and research of a new method of performance of an estimation of resistance of the cipher Rijndael to differential attacks offered by the Japanese scientists.