Revisiting Quantum Secure Direct Communication with W State

Abstract

The quantum secure direct communication protocol recently proposed byCao and Song [Chin. Phys. Lett. 23 (2006) 290] (i.e., the C-S QSDCprotocol) is revisited. A security leak is pointed out. Taking advantageof this leak, an eavesdropper may adopt the intercept–measure–resendstrategy to attack the quantum channel such that in the C-S QSDCprotocol the secret message can be completely eavesdropped. To fix theleak, the original version of the C-S QSDC protocol is revised. As aconsequence, the security is improved and assured at least in the caseof an ideal quantum channel.