The Design And Analysis Of Communication Protocols By Using Discrete-time Ouantum Walk

Recently,with the fast development of quantum parallel computing and quantum computer,classical encryption algorithms,whose security rely on computation complexity,are faced with serious challenges and the security of network communication cannot be ensured.Taking this problem into consideration,Quantum information technology,with the properties of entanglement and coherence superposition,can ensure the unconditional security of communication theoretically.Therefore,it is of great importance to design more secure and efficient communication schemes with quantum information technology.Discrete-time quantum walk,as a model,can be applied to designing various communication schemes,such as perfect state transfer and message authentication.On one hand,discrete-time quantum walk can be applied to realize perfect state transfer scheme based on different network models.On the other hand,we can design more secure Hash function based on discrete-time quantum walk.Furthermore,apply this kind of Hash function to message authentication scheme,which is of great importance during communication.In this dissertation,quantum walk is studied and utilized to more secure and efficient communication schemes.And our work is described as follows:(1)A scheme using a new kind of quantum walk is proposed to realize perfect state transfer on different quantum network models.We analyze this scheme from some aspects,then,some features and advantages can be concluded.In our scheme,firstly,the single-qubit states can be transferred from the source to the target by finite steps with fidelity and probability 1,which will make execution easier in practice.Secondly,due to fewer restrictions to the network models,our scheme can be adopted to more general network models,such as the butterfly network,the inverted crown network,the grail network and the generalized butterfly network Gk.Finally,in addition to single-qubit states,arbitrary two-qubit initial states can be transferred on different kinds of network models.(2)A new message authentication scheme is proposed based on quantum Hash function,where the Advanced Encryption Standard acts as encryption function and the new quantum Hash function acts as the authentication function.Firstly,the Advanced Encryption Standard algorithm is used to encrypt the result of the initial message cascading the corresponding Hash values,which ensures that the initial message can resist eavesdropping attack.Secondly,in existing quantum Hash function,researchers did not discuss about a problem that the length of some initial messages may be too short.Based on this problem,add some extra bits(generated randomly)to the initial messages to meet the requirements,which can make the initial messages resisting brute force attack.Furthermore,utilize the improved quantum Hash function with quantum walks as authentication function.Based on these two points,the message authentication scheme can be much more secure than previous ones.