In this paper we use the nonrepresentable ring E (m) p to introduce public key cryptosystems in noncommutative settings and based on the Semigroup Action Problem and the Decomposition Problem respectively.
IntroductionMost public-key cryptosystems are based on certain specific problems of number theory.One of these problems is the Integer Factorization Problem (IFP) over the ring Z n , being n the product of two large prime numbers; the well known cryptosystem RSA [22] is based in this problem. The second classical problem is the Discrete Logarithm Problem (DLP) over a finite field Z p , being p a large prime; the Diffie-Hellman key exchange protocol [9] and ElGamal protocol [10] are based on this problem. In general, we can say that their robustness depends on the computational difficulty of solving certain mathematical problems over finite commutative algebraic structures. Some efficient attacks based on the commutative property of these structures are well known: Quadratic Sieve, General Number Field Sieve, Pollard's rho algorithm, Index-Calculus, etc. (see, for example, [19,28], and the references within these books).This fact, together with the increase of the computational power of modern computers, has made these techniques become more and more insecure. As a result there exists an active field of research known as noncommutative algebraic cryptography (see, for example, [2,12,13,23,26]) aiming to develop and analyse new cryptosystems and key *