A Linear Cryptanalysis On Simplified Kuznyechik 2

This research focuses on the application of linear cryptanalysis to Simplified Kuznyechik 2 (S-KN2). This research aims to assess the vulnerability to linear attacks on the S-KN2 algorithm. This research applies linear cryptanalysis to the S-KN2 algorithm by finding the best bias value of the S-KN2 linear approximation for each active s-box in each round, which then derives a linear equation that can be used to find a key candidate that matches the expected key. In this study, we used 5000 samples of generated plaintext and ciphertext pairs to return the subkey values in the last round. As a result, the candidate keys have bias values that are close to the theoretical bias value divided by 10. Based on these results, it is assumed that the L-Transformation has an effect on the linear approximation of S-KN2, and further research is needed in that regard.