Self-stabilizing Byzantine Pulse and Clock Synchronization

This thesis presents a scheme that achieves self-stabilizing Byzantine digital clock synchronization assuming a “synchronous” system. This synchronous system is established by the assumption of a common external “beat” delivered with a regularity in the order of the network message delay, thus enabling the nodes to execute in lock-step. The system can be subjected to severe transient failures with a permanent presence of Byzantine nodes. The presented algorithms guarantee eventually synchronized digital clock counters, i.e. common increasing integer counters associated with each beat. Two algorithms for achieving this synchronization are given. The first one, produces digital clock synchronization directly. The second one, produces an underlaying pulse which can be used to create clock synchronization, or can be used for other synchronization goals. Using the digital clock synchronization, one can go on to achieve regular clock synchronization, progressing at real-time rate and with high granularity. In addition, a general Byzantine stabilizer is shown, based on the pulse synchronization algorithm. This thesis shows the first algorithms to achieve deterministic linear convergence time, supporting f < n 3 Byzantine nodes. In addition, it does not require the use of local physical timers. Moreover, it is the first to show a self-stabilizing protocol that overcomes Byzantine faults and operates in a network that is not fully connected.