Quantum Public-Key Cryptosystem Based on the Non-Locality in Unentangled Quantum System

A quantum public-key cryptosystem based on the non-locality in an unentangled quantum two-particle system is presented in this paper. Every user shares a set of quantum two-particle systems in orthogonal product states with a key management center (KMC) as the (public key, private key) pairs. By the help of KMC, users can accomplish secret communications. Message authentication can also be realized in the public-key cryptosystem. The laws of quantum physics guarantee the unconditional security of this cryptosystem. No entangled states or complex quantum operations are needed. In the communication process, any two users need not exchange quantum particles. So the public-key cryptosystem is easier to carry out in practice.