Byzantine agreement : algorithms and applications

All participating processes in a distributed system often have to reach agreement of some kind. The presence of malicious faults can cause a faulty process to send conflicting messages to different processes, making it difficult for nonfaulty processes to reach agreement. This problem, often called Byzantine agreement, Byzantine generals problem, or interactive consistency, is important in both the theory and practice of distributed computing and has been the subject of intense research in recent years. This thesis presents a comprehensive study of this problem and its various applications. The Mostly Byzantine agreement is proposed as a less restrictive model for process-control applications. It can achieve a high degree of fault tolerance with a relatively low cost.