Coral: Maliciously Secure Computation Framework for Packed and Mixed Circuits

Achieving malicious security with high efficiency in dishonestmajority secure multiparty computation is a formidable challenge. The milestone works SPDZ and TinyOT have spawn a large family of protocols in this direction. For boolean circuits, state-of-the-art works (Cascudo et. al, TCC 2020 and Escudero et. al, CRYPTO 2022) have proposed schemes based on reverse multiplication-friendly embedding (RMFE) to reduce the amortized cost. However, these protocols are theoretically described and analyzed, resulting in a significant gap between theory and concrete efficiency. Our work addresses existing gaps by refining and correcting several issues identified in prior research, leading to the first practically efficient realization of RMFE. We introduce an array of protocol enhancements, including RMFE-based quintuples and (extended) double-authenticated bits, aimed at improving the efficiency of maliciously secure boolean and mixed circuits. The culmination of these efforts is embodied in Coral, a comprehensive framework developed atop the MP-SPDZ library. Through rigorous evaluation across multiple benchmarks, Coral demonstrates a remarkable efficiency gain, outperforming the foremost theoretical approach by Escudero et al. (which incorporates our RMFE foundation albeit lacks our protocol enhancements) by a factor of 16-30×, and surpassing the leading practical implementation for Frederiksen et al. (ASIACRYPT 2015) by 4-7×. CCS Concepts • Security and privacy → Information-theoretic techniques.