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Mr NISC: Multiparty Reusable Non-Interactive Secure Computation

Authors:
Fabrice Benhamouda
Huijia Lin
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Abstract: Reducing interaction in Multiparty Computation (MPC) is a highly desirable goal in cryptography. It is known that 2-round MPC can be based on the minimal assumption of 2-round Oblivious Transfer (OT) [Benhamouda and Lin, Garg and Srinivasan, EC 2018], and 1-round MPC is impossible in general. In this work, we propose a natural ``hybrid'' model, called \emph{multiparty reusable Non-Interactive Secure Computation (mrNISC)}. In this model, parties publish encodings of their private inputs xi on a public bulletin board, once and for all. Later, any subset I of them can compute \emph{on-the-fly} a function f on their inputs x→I={xi}i∈I by just sending a single message to a stateless evaluator, conveying the result f(x→I) and nothing else. Importantly, the input encodings can be \emph{reused} in any number of on-the-fly computations, and the same classical simulation security guaranteed by multi-round MPC, is achieved. In short, mrNISC has a minimal yet ``tractable'' interaction pattern. We initiate the study of mrNISC on several fronts. First, we formalize the model of mrNISC protocols, and present both a UC security definition and a game-based security definition. Second, we construct mrNISC protocols in the plain model with semi-honest and semi-malicious security based on pairing groups. Third, we demonstrate the power of mrNISC by showing two applications: non-interactive MPC (NIMPC) with reusable setup and a distributed version of program obfuscation. At the core of our construction of mrNISC is a witness encryption scheme for a special language that verifies Non-Interactive Zero-Knowledge (NIZK) proofs of the validity of computations over committed values, which is of independent interest.
Video from TCC 2020
BibTeX
@article{tcc-2020-30637,
  title={Mr NISC: Multiparty Reusable Non-Interactive Secure Computation},
  booktitle={Theory of Cryptography},
  publisher={Springer},
  author={Fabrice Benhamouda and Huijia Lin},
  year=2020
}