Three-party quantum secure direct communication base on Partially Entangled States

In this paper, we point out Partially Entangled States quantum dialogue, which enables both legitimate parties to exchange their 2 bit secret messages in a direct way. Two step security check guarantees the security of this protocol. Partially Entangled States used as information carrier are easy to prepare and store, there is no need to transmit quantum states with secret message in quantum channel and two users can simultaneously communicate with the third party. The protocol is secure against the intercept-resend attack and the entangle-measure attack.