An efficient controlled bidirectional quantum secure direct communication by using only EPR pairs

Abstract

This paper proposes a bidirectional quantum secure direct communication protocol with a controller, who assists the users in making sure both sides could receive the other's secret messages simultaneously during the transmission. This protocol is based on Einstein-Podolsky-Rosen (EPR) pairs. If any eavesdropper tries to steal dealer's messages, the lawful participants will perceive it and abort their transmission.