Dual-velocity protocol of hybrid QKD system and its security analysis

Based on the hypothesis that the velocity of light in vacuum is the maximum velocity possible for any signal, we present a dual-velocity protocol for a hybrid quantum key distribution (QKD) system, and prove that its security is the same as that for the BB84 protocol. We show that this protocol can improve the efficiency of quantum key generation from 50% to 100%, and, at the same time, reduce Eve's information. Because it breaks the symmetry between Bob and Eve before open discussion, the dual-velocity protocol extends the concept of QKD and increases our choice of protocol bases. We present three application examples and analyze in detail their security under intercept/resend attacks.