Security of Quantum Key Distribution

H.-K. Lo, H. F. Chau


We construct a new quantum key distribution scheme and prove its security against the most general type of attacks and the most type of noises allowed by quantum physics. The novel technique we use is reduction from a quantum scheme to a classical scheme. We first show that, rather surprisingly, the proof of security of our quantum key distribution in the error-free case can be reduced to that of a classical verification scheme. In other words, the quantum verification procedure employed by us has a classical interpretation by proving the security of the classical scheme, the security of our quantum key distribution scheme in the error-free case follows immediately. The security against the most general types of noises (channel noises, storage errors, and computational errors) is then proven by using fault-tolerant quantum computation.Our result implies that, given quantum computers, quantum key distribution over an arbitrarily long distance of a realistic noisy channel can be made unconditionally secure.