On achieving the "best of both worlds" in secure multiparty computation
Jonathan I. Katz · 2007
Two settings are typically considered for secure multipartycomputation, depending on whether or not a majority of the partiesare assumed to be honest. Protocols designed under this assumptionprovide "full security" (and, in particular, guarantee outputdelivery and fairness) when this assumption is correct; however, if half or more of the parties are dishonest then security iscompletely compromised. On the other hand, protocols toleratingarbitrarily-many faults do not provide fairness or guaranteed output delivery even if only a single party is dishonest. It isnatural to wonder whether it is possible to achieve the "best ofboth worlds" : namely, a single protocol that simultaneouslyachieves the best possible security in both the above settings. Ishai, et al. (Crypto 2006) recently addressed this question, andruled out constant-round protocols of this type.