Paper 2024/035

A New Approach to Efficient and Secure Fixed-point Computation

Tore Kasper Frederiksen, Zama
Jonas Lindstrøm, Mysten Labs
Mikkel Wienberg Madsen, The Alexandra Institute
Anne Dorte Spangsberg, The Alexandra Institute

Secure Multi-Party Computation (MPC) constructions typically allow computation over a finite field or ring. While useful for many applications, certain real-world applications require the usage of decimal numbers. While it is possible to emulate floating-point operations in MPC, fixed-point computation has gained more traction in the practical space due to its simplicity and efficient realizations. Even so, current protocols for fixed-point MPC still require computing a secure truncation after each multiplication gate. In this paper, we show a new paradigm for realizing fixed-point MPC. Starting from an existing MPC protocol over arbitrary, large, finite fields or rings, we show how to realize MPC over a residue number system (RNS). This allows us to leverage certain mathematical structures to construct a secure algorithm for efficient approximate truncation by a static and public value. We then show how this can be used to realize highly efficient secure fixed-point computation. In contrast to previous approaches, our protocol does not require any multiplications of secret values in the underlying MPC scheme to realize truncation but instead relies on preprocessed pairs of correlated random values, which we show can be constructed very efficiently, when accepting a small amount of leakage and robustness in the strong, covert model. We proceed to implement our protocol, with SPDZ as the underlying MPC protocol, and achieve significantly faster fixed-point multiplication.

Note: This revision contains a note on how to use one of our preprocessing algorithms in the context of the probabilistic truncation of Catrina and Saxena in order to achieve somewhat similar results to ours.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Major revision. ACNS 2024
MPCfixed-pointmalicious securitycovert securityUCresidue number systems
Contact author(s)
tore frederiksen @ zama ai
jonas @ mystenlabs com
mikkel wienberg @ alexandra dk
a d spangsberg @ alexandra dk
2024-05-01: revised
2024-01-09: received
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      author = {Tore Kasper Frederiksen and Jonas Lindstrøm and Mikkel Wienberg Madsen and Anne Dorte Spangsberg},
      title = {A New Approach to  Efficient and Secure Fixed-point Computation},
      howpublished = {Cryptology ePrint Archive, Paper 2024/035},
      year = {2024},
      note = {\url{}},
      url = {}
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