STUDY OF THE STRENGTH OF AN AUTHENTIFIED ENCRYPTION ALGORITHM BASED ON SPONGE FUNCTION

Urgency of the research. In recent years, the direction of "cryptography of substitutions" has been formed in theoretical cryptography, which studies fixed substitutions of large dimensions as crypto-primitives. So-called sponge functions can be used in the implementation of this class of primitives.Target setting. One of the approaches to building authenticated encryption algorithms is to use sponge functions. In some countries (for example, in the Republic of Belarus and Malaysia) the development of national standards for cryptographic protection of information using authenticated encryption algorithms based on the sponge function Bash-f is being completed. In this regard, there is some interest in the study of this algorithm, especially to assess its resistance to attacks and evaluate its speed.Actual scientific researches and issues analysis. In modern research, a significant place is occupied by the problems of cryptographic protection of information. In the works of scientists widely various issues regarding the protection of information, including cryptographic are described, but the question of the stability of the algorithm of authenticated encryption based on the sponge function remains unexplored.Uninvestigated parts of general matters defining. At present, the work of domestic and foreign scientists has not studied the issue of resistance to standard attacks of the algorithm of authenticated encryption, based on the proposed by Belarusian scientists sponge-function Bash-f.The research objective. Investigate the resistance to standard attacks of the authenticated encryption algorithm, based on the sponge function Bash-f proposed by Belarusian scientists.The statement of basic materials. The use of iterative constructions such as sponge is an alternative approach in the construction of authenticated encryption algorithms. The main parameters by which the encryption algorithm is evaluated are usually its resistance to attacks aimed at decrypting the ciphertext (recovery of the encryption key), and the speed of the encryption process. In the case of the authenticated encryption algorithm, an assessment of its resistance to attacks is added, aimed at violating the integrity (forgery of imitations). As a rule, the stability of the algorithm is evaluated both to known general-purpose attacks, such as tradeoff-attacks, and to basic attacks developed specifically for the algorithm. The stability of the algorithm for different types of tradeoff-attacks is studied. Although the computational complexity of tradeoff attacks is less than brute force attacks, the amount of memory required and the number of prefixes for a successful attack is large enough. Therefore, its application in practice is unlikely. The stability of the algorithm was considered in accordance with the following basic attacks: search for ways; finding cycles; recovery; internal collision. The probability of success of basic attacks is determined by estimates from above on the stability of the sponge function, the minimum number of calls to F for a successful attack is О(2????+2). For key-dependent algorithm modes, ‘gamma prediction’ and ‘fake imitation’ attacks are considered. The expected number of appeals to F was О(2????/2), and at l≤c attacks do not pose a threat at all.Conclusions. The results obtained on the resilience of the investigated algorithm of authenticated encryption to both universal tradeoff-attack and basic attacks for sponge constructs confirm that it is stable. Given the previously obtained estimates of the speed of implementation of this algorithm, it can be argued that this class of algorithms based on the sponge function F may be promising for use in creating a secure cyberspace.