摘要
Two efficient protocols of quantum secure direct communication with authentication [Chin. Phys. Lett. 25 （2008） 2354] were recently proposed by Liu et al. to improve the efficiency of two protocols presented in [Phys. Rev. A 75 （2007） 026301] by four Pauli operations. We show that the high efficiency of the two protocols is at the expense of their security. The authenticator Trent can reach half the secret by a particular attack strategy in the first protocol. In the second protocol, not only Trent but also an eavesdropper outside can elicit half-information about the secret from the public declaration.
Two efficient protocols of quantum secure direct communication with authentication [Chin. Phys. Lett. 25 （2008） 2354] were recently proposed by Liu et al. to improve the efficiency of two protocols presented in [Phys. Rev. A 75 （2007） 026301] by four Pauli operations. We show that the high efficiency of the two protocols is at the expense of their security. The authenticator Trent can reach half the secret by a particular attack strategy in the first protocol. In the second protocol, not only Trent but also an eavesdropper outside can elicit half-information about the secret from the public declaration.
基金
Supported by the National High Technology Research and Development Programme of China under Grant No 2006AA01Z419, the National Natural Science Foundation of China under Grant Nos 90604023, 60873191 and 60821001, the National Laboratory for Modern Communications Science Foundation of China under Grant No 9140C1101010601, the Natural Science Foundation of Beijing under Grant No 4072020, and the ISN Open Foundation.
