  The security of the previous quantum key distribution (QKD) protocols, which
is guaranteed by the nature of physics law, is based on the legitimate users.
However, impersonation of the legitimate communicators by eavesdroppers, in
practice, will be inevitable. In fact, the previous QKD protocols is unsecure
without authentication in practical communication. In this paper, we proposed
an improved QKD protocol that can simultaneously distribute the quantum secret
key and verify the communicators' identity. This presented authentication
scheme is provably secure.
