joint work with Seny Kamara, Payman Mohassel |
Results: We initiate the study of secure multi-party computation (MPC) in a server-aided setting, where the parties have access to a single server that (1) does not have any input to the computation; (2) does not receive any output from the computation; but (3) has a vast (but bounded) amount of computational resources. In this setting, we are concerned with designing protocols that minimize the computation of the parties at the expense of the server. We develop new definitions of security for this server-aided setting, that generalize the standard simulation-based definitions for MPC, and allow us to formally capture the existence of dishonest but non-colluding participants. This requires us to introduce a formal characterization of non-colluding adversaries that may be of independent interest. We then design general-purpose server-aided multi-party protocols that are more efficient (in terms of computation and communication) for the parties than the alternative of running a standard MPC protocol (i.e., without the server). We give a general transformation from any secure delegated computation scheme to a server-aided two-party protocol. Our transformation formalizes the intuitive connection between the problems of server-aided computation and verifiable computation by interpreting the former as a means for verifiably and privately outsourcing a secure multi-party computation protocol to an untrusted worker. Finally, we construct a specialized protocol in the server-aided setting for the problem of set intersection with improved efficiency. |
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Resources: Outsourcing Multi-Party Computation Paper |