Security Analysis of the Multi-photon Three-stage Quantum Key Distribution

This paper presents a multi-stage, multi-photon quantum key distribution protocol based on the double-lock cryptography. It exploits the asymmetry in the detection strategies between the legitimate users and the eavesdropper. The security analysis of the protocol is presented with coherent states under the interceptresend attack, the photon number splitting attack, and the man-in-the-middle attack. It is found that the mean photon number can be much larger 1. This complements the recent interest in multi-photon quantum communication protocols that require a pre-shared key between the legitimate users.