TSS-BQS系统的Graceful Degradation机制

将门限签名方案分别应用于两种类型的BQS系统(Masking BQS系统和Dissemination BQS系统),可以得到两种TSS- BQS系统(文中称为TSS- mBQS系统和TSS- dBQS系统).TSS-mBQS系统的性能优于TSS- dBQS系统.由此,作者提出了TSS- BQS系统的Graceful Degradation机制:系统由n=3fd+1台服务器组成,在初始阶段以TSS-mBQS状态运行,容忍fm=fd/2]台Byzantine失效服务器；随着系统运行,可能失效的服务器数量增大,则以降低性能为代价,切换到TSS- dBQS状态,容忍fd台Byzantine失效服务器.在不影响容错能力的前提下,Graceful Degradation机制提高了已有TSS- BQS系统的平均性能.文中完成的Graceful Degradation机制能够在不中断存储服务、不影响客户端的前提下完成状态切换,客户端也不需要知道系统的运行状态(处于TSS- mBQS或TSS- dBQS状态).

Graceful Degradation in TSS-BQS Systems

By integrating threshold signature schemes with different types of Byzantine quorum systems(i.e.,masking BQS and dissemination BQS in this paper),we can build two TSS-BQS systems,called the TSS-mBQS system and the TSS-dBQS system.The TSS-mBQS system produces better performance than the TSS-dBQS one.Based on this observation,we design graceful degradation in TSS-BQS systems: In the beginning,the system consisting of n=3fd+1 servers,runs in the TSS-mBQS state and tolerates up to fm= ■fd/2」 Byzantine faulty servers;with the increasing number of servers which might be faulty,the system switches to the TSS-dBQS state,and tolerates up to fd Byzantine faulty servers at the cost of performance degradation.Without harming the system’s fault-tolerance,the graceful degradation improves its performance on average.Moreover,this graceful degradation doesn’t interrupt the storage services of the system,and is transparent to clients who don’t need to know the system state(i.e.,the TSS-mBQS or the TSS-dBQS state).