Qkd System Security Analysis And Development Of Strong Attenuation System

With the rapid development of IT and computer technology, information and communication securities become more important .Quantum communication is one of the most important technologies, which is the combination of quantum mechanics and cryptography. Quantum key distribution is based on the Heisenberg's uncertainty principle which guarantees that no eavesdropper can escaped detection .A linchpin technology of quantum key distribution is single photon which is foundation of security. Ideal single photon sources are far beyond real application. In practice, single photon sources being used are gained from precisely controlled heavy attenuation. To analyse the security of Quantum key distribution system based on practical single photon sources is being very important.Practical quantum key distribution systems and their securities are analysed and researched. A heavy attenuation system model easy to realize quantum communication web is put forward in the last .The achievements are as follows:1. Practical implementations of quantum key distribution systems use attenuated laser pulses as the signal source rather than single photons. The channels used to transmit are lossy. On the basis of above two points, a combining eavesdropping strategy of intercept-resend and beam-splitting is discussed in terms of eavesdropper's technology requirement and detection efficiency and dark count of single-photon counter. At last, a maximum disturbance bound is derived for a given mean photon number and transmission length. Eavesdropper can be detected with the bound.2. Several typical QKD systems are introduced and analyzed .QKD experiment is simulated in the laboratory. Al last, a new QKD(quantum key distribution)system based on interaction-free measurement is put forward.3. Optical attenuation, widely applied in many fields, can be adopted to acquire single-photon sequence that is foundational in quantum key distribution. We obtain single-photon sequence by precisely controlled optical power distribution along outlets of manifold consist of beam splitter instead of the attenuation by timesequence due to loss.