Maliciously Secure MPC From Semi-Honest 2PC in the Server-Aided Model

Secure multi-party computation (MPC) provides provable security guarantees for many privacy critical applications. The semi-honest MPC protocols are secure against semi-honest adversaries who can only observe the protocol execution, while the maliciously secure MPC protocols are secure against malicious adversaries who can deviate from the protocol description arbitrarily. Many security sensitive applications tend to use semi-honest MPC protocols because malicious security comes with huge communication and/or computation costs. In this work, we show how to efficiently transform generic semi-honest two-party protocols into maliciously secure multi-party protocol in the server-aided setting. We further propose an optimized constant-round server-aided MPC protocol. The proposed protocols are secure when all but one parties are maliciously corrupted, while the remaining party and the server are corrupted by semi-honest and non-colluding adversaries. We implement and evaluate our constant-round protocol. For the 2-party case, our protocol is only 1.11&#x00D7; slower than the <italic>semi-honest</italic> Yao&#x0027;s Garbled Circuits protocol, and it is 9.16&#x00D7; faster than the maliciously secure authenticated garbling protocol and 4.96&#x00D7; faster than the state-of-the-art maliciously secure server-aided protocol of Wu et al. For the 8-party case, our protocol is 103.29&#x00D7; faster than the authenticated garbling protocol and 17.03&#x00D7; faster than the protocol of Wu et al.