Security Analysis And Computer Simulation Based On Quantum Key Distribution Protocols

From ancient times to the present, the communication security enjoys high significance. In the modern communication society, there is wide spread need of secure transmission of secret information, such as the commercial trade and the communication in network, which need to be on the guard of the attack of the eavesdropper. In the meantime, with the rapid development of information technology, the methods of decryption are even more brilliant. It is believed that in modern cryptography, any algorithm of encryption and decryption in cryptographical systems could be public, and the security should rely on the secure key. In classical cryptography, because of the passive eavesdropping, the absolute security of secure key is impossible, nevertheless, quantum cryptography, which is based on quantum physics, has been proved to be an effective technique for secure key distribution. The eavesdropper cannot measure the signal without disturbing them.In this thesis, the BB84 protocol and B92 protocol are explained at some length. The realization issues of these protocols important for the security aspect are discussed, and we analyzed their security. The analysis showed that these protocols were absolutely safe under the non-noise circumstances. However, because of the objective factors, such as the detector noise and misalignments, it is very important to make a detailed study of the attacking methods for the sake of practicality. The information the eavesdropper gained through interception is a very important criterion for judging the success of the key transmission, so we analyzed the information volume based on BB84 and B92 protocols when the cryptographical systems were attacked.In the latter part of this thesis, the simulation of quantum cryptography on classical computer was discussed in detail. With the quantum key distribution becoming a hot topic in the information-security field, the realization methods of quantum cryptography were more concerned by researchers. In this thesis,methods to express the preparation and measurement of quantum states on current computer and the basic algorithm for simulating the quantum key distribution protocols were given, and the programs for simulating the quantum key transmission were given. The keys gained from quantum key distribution system were used for image encoding. Finally, we simulated the quantum key distribution system and image encoding on Visual C++ 6.0 platform. All the corresponding results of BB84 protocol were presented and compared with the theoretic results. It was shown that the simulation results were completely tailed with theoretic ones.