Cryptanalysis of a key exchange protocol based on the ring $$E_p^{(m)}$$ E p ( m )

Abstract

An extension of Bergman’s ring (Israel J Math 18:257–277, 1974) was introduced by Climent et al. (Appl Algebra Eng Commun Comput 23:347–361, 2014). For this ring called \(E_p^{(m)}\), they established that only a negligible fraction of elements are invertible, and then proposed a key exchange protocol based on this property. Shortly afterwards, they constructed another key agreement protocol for multicast over this ring (WIT Trans Inf Commun Technol 45:13–24, 2013). In this paper, we introduce a polynomial-time attack to these two protocols without using invertible elements.