%0 Journal Article %T Cryptanalysis of some protocols using matrices over group rings %A Mohammad Eftekhari %J Computer Science %D 2015 %I arXiv %X We address a cryptanalysis of two protocols based on the supposed difficulty of discrete logarithm problem on (semi) groups of matrices over a group ring. We can find the secret key and break entirely the protocols. %U http://arxiv.org/abs/1503.04779v1