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In this paper we provide a quantum authentication protocol. It is based on the nonlocality of the orthogonal product states of a two-particle system. The two parties share a sequence of two-particle systems as the authentication key. To authenticate each other, they only need to create auxiliary particles and exchange them. No one without the authentication key can pass the authentication process. So the protocol is secure. The authentication key is reusable because it doesn't change after the authentication process. The protocol is more practicable because it needn't entangled states and complex operations but product states and measurement which are easier to carry out in practice.