We reply to the preceding comment which focused on whether there exists a quantum privacy amplification technique for purifying the unknown single-photon states transmitted. In this Reply, we will show that quantum privacy amplification is principally possible, and a specific scheme for direct communication protocol based on single photons has been constructed and will be published elsewhere. Then the secure direct quantum communication is secure against the attack strategy in the preceeding comment by using quantum privacy amplification directly.

• Received 18 January 2005

DOI:https://doi.org/10.1103/PhysRevA.72.016302