The primary objective of this work is to develop an algorithm for detecting the secret round key used in encryption by analyzing a collection of plaintexts and ciphertexts encrypted with the three-round Kuznyechik algorithm. In addition, the fundamentals of using the integral cryptanalysis method for the Substitution-permutation (SP) network-based Kuznyechik encryption have been investigated. It has been found that the Kuznyechik three-round encryption algorithm is useful for creating a balanced set before the third round and an unbalanced set at the end of the round, using a set in which the first byte is active, and the remaining bytes are passive. Based on the findings above, an efficient algorithm to determine the key of the final round for the 3-round Kuznyechik algorithm is proposed utilizing the method of integral cryptanalysis. According to simulation results, the proposed approach offers approximately 90% improvement compared to baseline algorithms in terms of time complexity, data, and memory overhead.

In order to study the impact of the proposed NSA(New stream algorithm) algorithm reflections on the selection of security parameters, research was carried out, in which analysis methods and data presented in the literature were used. The output function of the NSA algorithm provides the 64-bit as the output value after the t-round. This requires investigating how small changes in input affect the NSA output function. Choosing any other array as the output array is easy to crack. Mazkur maqolada taklif etilgan NSA(New stream algoritm) algoritmi akslantirishlarining tanlanishida xavfsizlik parametrlariga ta’sirini o‘rganish maqsadida tadqiqotlar o‘tkazildi, bunda adabiyotlarda keltirilgan tahlil usullari va ma’lumotlardan foydalanildi. NSA agoritmining chiqish funktsiyasi 64 bitli a2(t) ni t - raunddan so‘ng chiqish qiymati sifatida taqdim qiladi. Bunda NSA chiqish funksiyasiga kirishdagi kichik o‘zgarishlar qanday ta’sir etishini tekshirish talab etiladi. Chiqish massivi sifatida boshqa har qanday massiv tanlanganda shifrni osongina buzish mumkin bo‘ladi.