Intercept-resend attack on passive side channel of the light source in BB84 decoy-state protocol

Abstract

Quantum key distribution (QKD) promises unconditionally secure communication based on fundamental laws of physics, though practical realizations of QKD may have loopholes and side channels, thus their security can be compromised. We analyze the intercept-resend attack on the BB84 decoy-state protocol under the presence of a passive side channel of the light source. We derive an upper bound for the secret key rate and show that it does not significantly deviate from the ideal side-channel-free case.