Oblivious and fair server-aided two-party computation

We show efficient, practical (server-aided) securetwo-party computation protocols ensuring privacy, correctnessand fairness in the presence of malicious (Byzantine) faults. Ourrequirements from the server are modest: to ensure privacyand correctness, we only assume offline set-up prior to protocolexecution; and to also ensure fairness, we further assume atrusted-decryption service, providing decryption service usingknown public key. The fairness-ensuring protocol is optimistic, i.e., the decryption service is invoked only in case of faults. Bothassumptions are feasible in practice and formally presented inthe hybrid model. The resulting protocols may be sufficientlyefficient, to allow deployment, in particular for financial applications.