Simulation And Test Of Quantum Cryptography Protocol

Quantum cryptography is a new cryptogram system, which can realize unconditionally secure communication, based on classic cryptography and quantum mechanics, Quantum cryptography protocol is a series of steps that the two parties and more than two parties accomplish some cryptogram mission by quantum rule. Quantum cryptography protocol includes quantum key distribution (QKD) protocol, quantum secret sharing (QSS) protocol, quantum identity authentication (QIA) protocol, quantum secure direct communication (QSDC) protocol and quantum signature (QS) protocol.The QKD protocols are run on different noisy quantum channels by simulation. For this, a new algorithm of the models of noisy quantum channels is advanced. The aim is to determine the grade of security and efficiency of the protocols in function of the parameters they are using by the algorithm; and also to propose a method for selecting the best parameters of protocols on a given channel. And we can improve the performances of the protocols on noisy channels. For example, when BB84 run on the phase-damping and amplitude-damping channel, by the change of probability that selecting the two groups of bases with, we can find a probability (having relation to p ) that the efficiency and security are better than the classic BB 84 's; when B92 run on the phase-damping channel by the change of the angle between two quantum states, we can find an angle(having relation to p ) that having a better efficiency and security too.Quantum cryptography is unconditionally secure. Because in practical quantum cryptogram system, the protocols and apparatuses are not on perfect states and have some bugs, Attacks happen. Such as incoherent attack, coherent attack, photon-number-splitting (PNS) attack, Trojan horse attack. Working over the attacks, we find their characteristics and advance the corresponding method to avoid them, and the secure communication realized.Quantum secure communication protocol is a kind of cryptographic protocol using quantum effects to provide unconditionally secure information exchange. We present a quantum secure direct communication protocol and a multiparty quantum secret sharing protocol based on Einstein-Podolsky-Rosen pairs and entanglement swapping. In both the protocols, The present quantum secure direct communication protocol makes use of the ideal of block transmission. Different to the proposed quantum secure direct communication protocols, the sender can encode his or her secret message as one of the four Bell states without ensuring the security of the quantum channel firstly. In the multiparty quantum secret sharing protocol, the communication parties adopt checking mode or encoding mode with a certain probability. It does not need multi-particles entangled state but only Einstein-Podolsky-Rosen pair to realize the protocol. Compared with the proposed quantum secret sharing protocol with entanglement swapping, it is not necessary for the protocol to perform local unitary operation. The efficiency for the protocol is greatly improved. The securities for both the protocols are the same as that for BBM92 protocol. But the protocols may be harmed by some attacks in application, such as man-in-middle attack, Trojan horse attack. It advances some methods to improve the situation.