9004 Problems of information security. Computer systems Проблемы информационной безопасности. Компьютерные системы 2071-8217 14 10.48612/jisp/3p1p-bx2v-prru On the question of the applicability of the statistics of the measure “chi-square” in the problem of determining the parameters of block encryption algorithms К вопросу о применимости статистик меры «хи-квадрат» в задаче определения параметров блочных алгоритмов шифрования 0000-0002-5606-7509 Mironkin Vladimir mironkin.v@mail.ru Yurasov Nikita n.yurasov@yahoo.com MIREA – Russian Technological University National Research University Higher School of Economics 30 09 2025 3 180 191

The article presents the results of the practical application of statistical methods for analyzing block encryption algorithms operating in the ECB encryption mode. In particular, in cases of incorrect use of plaintext encoding algorithms, it is established that it is possible to determine the block size of encryption algorithm based on the analysis of chi-square statistics calculated on the available ciphertext volume.

 Block encryption algorithm encryption mode ECB mode statistics criterion chi-squared distribution