Research Of Quantum Digital Signature Scheme Based On The BB84 Protocol

Digital signatures are considered to be one of the most important inventions of modern cryptography,which are mainly used to ensure the integrity of information in communication and the identity of the sender.However,the security of classical signature protocols relies on difficult computational problems such as finding discrete logarithms or factoring large primes.Nowadays,with the development in computer technology and the proposal of quantum algorithms,digital signatures will face security problems.Under this circumstance,the idea of quantum digital signatures has been proposed to ensure the security of signature information.In principle,the unconditional security of quantum digital signatures can be guaranteed by the fundamental principles of quantum mechanics.This thesis firstly introduces the background and research progress of quantum digital signatures.Then the quantum key distribution protocol used in quantum digital signatures is described,the unconditional security of quantum key distribution and BB84 protocol are mainly introduced,followed by the introduction of the decoy-state method to resist the photon number splitting attack,and then describes the protocol process and security analysis of the quantum digital signature method based on BB84 protocol.The quantum digital signature method based on BB84 protocol has made progress in theory and experiment in recent years,but still faces many challenges,such as low signature rate,short safe transmission distance,and difficult experimental operation.This thesis mainly proposes corresponding remedies for these defects,which can be summarized in the following two aspects:1.Since there is no ideal single photon source,most previous theoretical and experimental studies on quantum digital signatures have used weak coherent sources.However,the non-negligible vacuum component and multi-photon component of weak coherent sources lead to the limitation of signature rate and safe transmission distance.To solve this problem,we study the single-photon-added coherent sources and apply the source to the three-intensity decoy state quantum digital signature protocol.The results show that this scheme is better than the scheme with weak coherent sources in terms of the signature rate and the safe transmission distance,which provides a great reference value for improving the performance of the quantum digital signature protocol based on BB84.2.In view of the difficulty of implementing the signature scheme,we propose a single decoy state quantum digital signature method.This method only needs to modulate the intensity of the source into two kinds of intensity,namely the signal state and the decoy state,so as to carry out efficient parameter estimation and quantum digital signatures.This method avoids the requirement of preparing vacuum state in the traditional multi-intensity decoy-state quantum digital signature scheme and reduces the difficulty of experimental implementation.At the same time,we carry out relevant numerical simulations,and the result shows that the one-decoy state quantum digital signature scheme has a higher signature rate compared with the two-decoy state scheme in a certain transmission distances.In practical applications,it is expected to optimize the actual performance of the system by using different decoy state methods according to different experimental conditions.Therefore,our work provides valuable references for the practical application of quantum digital signatures.