Abstract: With the emergence of various blockchain systems,the demand for cross-chain interaction is increasing,and the security of cross-chain bridge verification becomes more and more important.The notary schemes have simple principle and high efficiency,and are often used in cross-chain transaction verification,cross-chain transaction confirmation and other processes.How-ever,the notary schemes have some problems,such as low degree of decentralization,verifiable transactions with low signature ratio,and information disclosure of verification nodes.In order to improve the security of cross-chain bridge verification,a time rotation notary group model based on threshold signature is proposed.The notary group in this model is composed of high credibility nodes that have both source and target blockchain accounts.The verification nodes in the notary group have tenure requirements and need to pledge the security deposit.The notary group uses threshold signature technology to sign cross-chain transactions.The cross-chain transaction can only be implemented after more than half of the verification nodes in the notary group sign.The candidate notary group provides some new verification nodes for the time rotation notary group.The analysis results of the time rotation notary group model proves that the proposed model has high degree of decentralization,low malicious attack rate of the verification nodes,high security of the verification signature links,high privacy of the verification nodes,and high efficiency of cross-chain message verification.

Key words: Blockchain, Cross-chain, Cross-chain bridge, Notary schemes, Threshold signature