Security of classical noise-based cryptography

摘要

We examine the security of a protocol on cryptographic key distribution proposed by Yuen and Kim (Yuen H P and Kim A M 1998 Phys. Lett. A 241 135). Theoretical and experimental analysis shows that, even if the eavesdropper can receive more photons than the legitimate receiver, secure key distribution is possible as long as the signal-to-noise ratio of the eavesdropper does not exceed eight times (9 dB) that of the receiver. Secure key distribution was demonstrated using conventional fibre optics. The secure key transmission rate in the experiment was estimated to be 2 Mb s~(-1) at its maximum (0.04 bit per sender's bit). The present protocol has advantages over other quantum key distribution protocols in that it is more efficient and more easily implemented, but careful design and management are necessary to ensure the security of the cryptosystem.