Gradient Cryptanalysis of Block Cipher CHAM 64/128

摘要

We^{1 provide the results of cryptanalysis of the lightweight block cipher CHAM 64/128 carried out by means of a so-called gradient statistical attack. The experiments show that after 23 rounds the secret key can be determined with probability 0.01 under the length of the input sample 231 bytes and complexity 237 round function evaluations. Theoretical extrapolation of the suggested attack shows that the key can be completely determined with probability 0.01 after 57 rounds. The recommended number of rounds for CHAM 64/128 is 80. According to the cipher designers, the most successful attack has been a related-key boomerang attack which is effective on 56 rounds.}