A String-Based Public Key Cryptosystem

Traditional methods in public key cryptography are based on number theory, and suffer from problems such as dealing with very large numbers, making key creation cumbersome. Here, we propose a new public key cryptosystem based on strings only, which avoids the difficulties of the traditional number theory approach. The security mechanism for public and secret keys generation is ensured by a recursive encoding mechanism embedded in a quasi-commutativerandom function, resulted from the composition of a quasi-commutative function with a pseudorandom function. Due to the inherent construction algorithm of the the proposed cryptosystem, the resulted mathematical inversion problem is likely to be harder than the classical discrete logarithm or integer factorization problems. Furthermore, the proposed cryptosystem is immune against the known quantum algorithm attacks.