Byzantine agreement with homonyms

Carole Delporte-Gallet, Hugues Fauconnier, Rachid Guerraoui, Anne-Marie Kermarrec, Eric Ruppert, Hung Tran-The
2011 Proceedings of the 30th annual ACM SIGACT-SIGOPS symposium on Principles of distributed computing - PODC '11  
So far, the distributed computing community has either assumed that all the processes of a distributed system have distinct identifiers or, more rarely, that the processes are anonymous and have no identifiers. These are two extremes of the same general model: namely, n processes use different authenticated identifiers, where 1 ≤ ≤ n. In this paper, we ask how many identifiers are actually needed to reach agreement in a distributed system with t Byzantine processes. We show that having 3t + 1
more » ... entifiers is necessary and sufficient for agreement in the synchronous case but, more surprisingly, the number of identifiers must be greater than n+3t 2 in the partially synchronous case. This demonstrates two differences from the classical model (which has = n): there are situations where relaxing synchrony to partial synchrony renders agreement impossible; and, in the partially synchronous case, increasing the number of correct processes can actually make it harder to reach agreement. The impossibility proofs use the fact that a Byzantine process can send multiple messages to the same recipient in a round. We show that removing this ability makes agreement easier: then, t + 1 identifiers are sufficient for agreement, even in the partially synchronous model.
doi:10.1145/1993806.1993810 dblp:conf/podc/Delporte-GalletFGKRT11 fatcat:cneitujhavcifhplnq6h4ymvsu