Cryptology ePrint Archive: Report 2020/1346

SodsMPC: FSM based Anonymous and Private Quantum-safe Smart Contracts

Shlomi Dolev and Ziyu Wang

Abstract: SodsMPC is a quantum-safe smart contract system. SodsMPC permissioned servers (verification nodes) execute contracts by secure multi-party computation (MPC) protocols. MPC ensures the contract execution correctness while trivially keeping the \textit{data privacy}. Moreover, SodsMPC accomplishes the contract \textit{business logic privacy} while protecting the contract user \textit{anonymous identity} simultaneously. We express the logic of a contract by a finite state machine (FSM). A state transition of the FSM is represented by a \textit{blind polynomial} with secret-shared coefficients. When using MPC to compute this blind polynomial, the contract business logic privacy is obtained. These coefficients which control the logic are binary secret shares. We also propose a base conversion method among binary and integer secret shares by MPC. Our contract anonymity comes from the ``mixing-then-contract'' paradigm. The online phase of the SodsMPC mixing is a multiplication between a preprocessed permutation matrix and an input vector in the form of secret sharing, which accomplishes a fully randomized shuffle of the inputs and keeps the secret share form for the following contract execution. All SodsMPC components, including a verifiable secret sharing scheme, are quantum-safe, asynchronous, coping with $t<n/3$ compromised servers, and robust (tolerates Byzantine servers) in both preprocessing and online phases.

Category / Keywords: cryptographic protocols / Multi-party Computation, Private Smart Contract, Finite State Machine, Anonymous Mixing, Quantum-safety

Date: received 26 Oct 2020

Contact author: wangziyu at buaa edu cn,dolev@cs bgu ac il

Available format(s): PDF | BibTeX Citation

Version: 20201029:145201 (All versions of this report)

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