Study On Quantum Multi-proxy Blind Signature Protocols

Nowadays,with the increasing level of information technology,applications such as the Internet,instant messaging and e-commerce all involve information security,which in turn is of vital interest to everyone.Encryption of information is one of the most important ways to ensure information security.Digital signatures are used to identify the signer and to verify that the information has not been tampered with,and in the communication process,to provide authentication services and anti-denial services,etc.Since the advent of digital signatures to date,a variety of signature methods have been proposed,the security of which is generally guaranteed by mathematically difficult problems,for example,the discrete logarithm problem over the domain of prime numbers,the elliptic curve problem,and the factorisation problem for large unity numbers.With the rapid development of quantum technology,all these problems may be quickly cracked in a short time.Quantum signatures can be seen as an extension of classical digital signatures,and as an important branch of quantum cryptography,will play an essential role in the next generation of cryptography.In this thesis,we combine the qualities of multiple agent signatures and blind signatures to address the problems of low efficiency and low attention to entangled states such as W state and cluster state in existing quantum signature schemes.The aim of this thesis is to improve the forgery resistance,non-repudiation and efficiency of signatures,and the main findings are described below.1.A quantum multi-proxy blind signature scheme with unordered signatures is proposed.Both the signature and verification processes are operated using the unitary operation,and the key is generated by the BB84 protocol or the B92 protocol to ensure the unconditional security of the scheme.In contrast to the curing process of current multi-agent signature schemes,which require sequential signatures,this scheme has no restriction on the order of signatures,which greatly improves the efficiency of the signature process.The scheme security analysis is presented in three aspects,proving that the scheme is resistant to certain attacks and is blind,unforgeable and undeniable.2.A multi-proxy signature scheme based on W state is proposed.Compared with the GHZ state mostly used in existing schemes,the W state is not in the 3-particle maximum entanglement state,but it is more robust than the GHZ state and can maintain entanglement better in the presence of particle loss,so using it in signature schemes will give better results.The original signer of this scheme first authorises the proxy signer to sign,followed by the proxy signers separately,and finally a trusted third party signature for signature verification.Moreover,the scheme requires only single-particle measurements and does not require the use of the unitary operation.3.A quantum multi-proxy blind signature scheme based on cluster states is proposed.Cluster states have the properties of GHZ states and W states,while also having maximum connectivity and continuous entanglement.In view of this,this scheme first uses a 4-particle cluster state as a quantum channel to achieve quantum teleportation.After the original signer performs a CNOT operation on the particle in its own hand,it performs a Bell measurement and authorizes the proxy signers to sign.The proxy signers then perform Bell measurements on the particles in their hands as signatures.Finally the verifier performs an appropriate measurement comparison operation to verify that the signature is valid.By comparing with existing related schemes,this scheme requires only4-particle cluster states as quantum channels,uses less resources and is more efficient in terms of signatures.