Feasibility of Double-Click Attack on a Passive Detection Quantum Key Distribution System

An eavesdropper (Eve) can exploit all the imperfections of a practical quantum key distribution (QKD) system to obtain some information about the secret key, no matter whether these imperfections are from the physical layer or from the post-processing layer. We propose a possible attack on a passive detection QKD system based on the imperfection from the software layer. The analysis shows that Eve can obtain all the information about the key without being discovered.