Paper 2019/599

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

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


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.

Note: Minor typo pointed out by William Koch

Available format(s)
Publication info
Published elsewhere. Minor revision. 2019 IEEE Symposium on Security and Privacy (SP)
MPCDecision TreesSVMRings
Contact author(s)
escudero @ cs au dk
2020-11-27: revised
2019-06-02: received
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Creative Commons Attribution


      author = {Ivan Damgård and Daniel Escudero and Tore Frederiksen and Marcel Keller and Peter Scholl and Nikolaj Volgushev},
      title = {New Primitives for Actively-Secure {MPC} over Rings with Applications to Private Machine Learning},
      howpublished = {Cryptology ePrint Archive, Paper 2019/599},
      year = {2019},
      doi = {10.1109/SP.2019.00078},
      note = {\url{}},
      url = {}
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