Research On Multi-signature Algorithm Based On Blockchain

Blockchain technology has gained wide attention from academia and industry because of its unique features of decentralization,de-trusting,immutability,and traceability,which can realize trustworthy data sharing and peer-to-peer value transmission by multiple parties without a trust base.In blockchain,all completed transactions need to be signed and then stored to validate the transactions,and it becomes a challenging problem to enhance the scalability of digital signatures in blockchain.Amongst others,the size of the digital signature of a blockchain transaction and the computational cost of verifying the signature are the main factors limiting the scalability of the signature.Multi-signature technology allows a group of signers to sign the same message,resulting in a single common signature-sized signature result.Therefore,the use of a multi-signature scheme can effectively reduce the total number of digital signatures,improve the efficiency of digital signature verification and ease network bandwidth.During the construction of a digital library,the use of digital information in a network environment requires the approval of all copyright owners.A multiple signature scheme can request the aggregation of digital signatures of all copyright owners into a single signature signed in a digital document for copyright protection when a user requests the use of a certain digital information.Based on different application scenarios,this thesis proposes an improved broadcast multi-signature scheme based on the Schnorr scheme and a serialize multi-signature scheme based on the BLS scheme.The specific work is as follows.(1)The improved Schnorr broadcast multi-signature scheme is proposed based on the multisignature application scenario in blockchain where there is no signature order requirement.To solve the problem of excessive communication in it,this thesis changes the process of usergenerated random numbers to one in which the smart contract generates random numbers and calculates the sum of the first part of the commitment values of the multiple signatures,thus saving the overhead of communication and calculation of commitment values.(2)The improved Schnorr broadcast multi-signature scheme is deployed to the real blockchain platform Hyperledger Fabric,and the scheme is modified based on the real blockchain Fabric platform.In the Fabric,the chaincode generates random numbers for the multi-signature users and uses the public key of each user in the set of participating public keys to elliptically encrypt the random numbers and record the set of participating public keys into the state of the world,ensuring that the users who obtain the random numbers are the participating users,thus eliminating the need to calculate the hash of the signer's unique number in the set of signatures in advance.Test experiments are done in this paper to verify the usability of the proposed scheme and the efficiency of signing and verification.(3)Based on the application scenario of multi-signature with signature order requirement in blockchain,a serialize multi-signature scheme based on BLS is proposed.By adding generating elements to the hash operation,the power calculation of the bilinear operation in the original scheme is changed to a summation calculation on the group,reducing the computational cost spent on signature verification.This thesis presents a detailed security proof for the proposed resignature scheme and applies the serialize multi-signature scheme to the approval process in egovernment,giving an implementation scheme based on the blockchain platform.