Cryptology ePrint Archive: Report 2019/599

New Primitives for Actively-Secure MPC over Rings with Applications to Private Machine Learning

Ivan Damgård and Daniel Escudero and Tore Frederiksen and Marcel Keller and Peter Scholl and Nikolaj Volgushev

Abstract: At CRYPTO 2018 Cramer et al. presented SPDZ2k, a new secret-sharing based protocol for actively secure multi-party computation against a dishonest majority, that works over rings instead of fields. Their protocol uses slightly more communication than competitive schemes working over fields. However, their approach allows for arithmetic to be carried out using native 32 or 64-bit CPU operations rather than modulo a large prime. The authors thus conjectured that the increased communication would be more than made up for by the increased efficiency of implementations.

In this work we answer their conjecture in the affirmative. We do so by implementing their scheme, and designing and implementing new efficient protocols for equality test, comparison, and truncation over rings. We further show that these operations find application in the machine learning domain, and indeed significantly outperform their field-based competitors. In particular, we implement and benchmark oblivious algorithms for decision tree and support vector machine (SVM) evaluation.

Category / Keywords: MPC, Decision Trees, SVM, Rings

Original Publication (with minor differences): 2019 IEEE Symposium on Security and Privacy (SP)

Date: received 29 May 2019, last revised 27 Nov 2020

Contact author: escudero at cs au dk

Available format(s): PDF | BibTeX Citation

Note: Minor typo pointed out by William Koch

Version: 20201127:171653 (All versions of this report)

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