In most traditional quantum public-key cryptosystems, the public key held by the key management center (KMC) is a group of quantum systems. The public key is destroyed after a secret communication process, and so users must reconstruct the public key with the KMC after every communication process or hold many copies of the public key in the beginning. This requirement is an obstacle to the practical application of such quantum cryptosystems. This paper describes a quantum public-key cryptosystem with reusable keys using entangled states. Each user shares a set of entangled quantum systems with the KMC as that individual user’s (public key, private key) pair. Two users can exchange secret communications with the help of the KMC. Moreover, the states of the quantum systems revert to their original states. The user’s (public key, private key) pair is unchanged so that the keys are reusable. It is unnecessary for users to reconstruct the public key with the KMC or save many copies of the public key in the KMC. As a result, this public-key cryptosystem is much less expensive to manage and easier to realize in practice than most traditional quantum public-key cryptosystems.
Li et al. (Mon,) studied this question.