Hacking on a quantum random number generator based on vacuum fluctuation

• 1、State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876

Abstract：Due to the notable advantages: easy to prepare vacuum state, insensitive to the detection efficiency, the detected variables can be quantized into multiple bits, etc., quantum random number generatorbased on vacuum fluctuation has become a popular practical quantum random number generator. In recent years,researches on its practical security generally assume stable local oscillatorand ideal homodyne detection, which will ignore potential practical security problems such as fluctuation of the local oscillator and imperfect homodyne detection. To study these problems, based on the principle of homodyne detection and the theory of conditional min-entropy, moreover considering theinfluence of the local oscillatorfluctuation, and the nonideal beam splitter and photodiodes, a theoretical hacking model is established. With theoretical simulations of the model, the number of random bits which are accessible tothe hacker , and the threat level to the security of the system are analyzed by supposingthat the hacker has the full ability to manipulate the unbalance of the homodyne detection without being found.The simulation results show that when the unbalance of the homodyne detection increases, the hacker can obtain more or even all random bits. Furthermore, this work will provide a beneficialreference for the subsequent hacking against the practical system.

Keywords： Theoretical physics, Optics Quantum random number Homodyne detection Min-entropy Hacking