TSS-BQS系统的GracefulDegradation机制

Graceful Degradation in TSS-BQS Systems

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=f2d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fm=■fd/2」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).

Abstract 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 pro- duces 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=3fa＋l servers,runs in the TSS-mBQS state and tolerates up to fm=「fd/2」Byzantine faulty servers~ with the in-creasing 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 aver- age. 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）.