On the limitations of universally composable two-party computation without set-up assumptions

摘要: The recently proposed universally composable (UC) security framework, for analyzing of cryptographic protocols, provides very strong guarantees. In particular, a protocol proven secure in this framework is guaranteed to maintain its even when deployed arbitrary multi-party, multi-protocol, multi-execution environments. Protocols securely carrying out essentially any task way exist, both the case an honest majority (in plain model, i.e., without set-up assumptions) and no common reference string model). However, little was known and, important special two-party protocols. We study feasibility function evaluation model. Our results show that few functions can be computed model so as provide UC Specifically, deterministic functions, we full characterization computable (Essentially, these are depend on at most one parties' inputs, furthermore "efficiently invertible" sense defined within.) For probabilistic only those where parties uniquely determine joint output.