The 24th Privacy Enhancing Technologies Symposium (PETS24)

Nan Wang#, Dongxi Liu

FlashSwift is a logarithmic-sized zero-knowledge range argument in the discrete logarithm setting without using a trusted setup. By combining the techniques from both Flashproof and SwiftRange, FlashSwift inherits and capitalizes on their efficiency advantages. It creates two new records of the smallest proof sizes, 289 bytes and 417 bytes, for 8-bit and 16-bit ranges among all the bit-decomposition-based range proofs without requiring trusted setups. Moreover, it is the first configurable range proof that is adaptable to various scenarios with different specifications.

The 45th IEEE Symposium on Security & Privacy (IEEE S&P24, Oakland)

Nan Wang#, Sid Chi-Kin Chau, Dongxi Liu

SwiftRange is a logarithmic-sized zero-knowledge range argument in the discrete logarithm setting without using a trusted setup. It is tailored for confidential transactions (CT) on blockchain platforms. It aims to prove a committed value lies in the range [0, 2^N-1], where N is the bit length of the range size. It achieves double verification efficiency of Bulletproofs at a lesser cost of communication for CT-friendly ranges, where N is 32 or 64.

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The 28th Annual International Conference on the Theory and Application of Cryptology and Information Security (ASIACRYPT 2022)

Nan Wang#, Sid Chi-Kin Chau

Flashproofs are efficient zero-knowledge proofs of knowledge in the discrete logarithm setting without using a trusted setup. They feature sub-linear efficiency in both communication and verification:

• The zero-knowledge range argument aims to prove a committed value lies in the range [0, 2^N-1], where N is the bit length of the range size. It achieves O(N^(2/3)) efficiency in both communication and verification. Especially, the high verification efficiency makes it a suitable candidate for smart-contract blockchain platforms, whose verification consumes comparable gas costs to that of the most efficient zk-SNARK (Groth16) that relies on a trusted setup.

• The zero-knowledge polynomial evaluation argument aims to prove that two committed values satisfy a public polynomial relation. It achieves logarithmic efficiency in both communication and verification and is a crucial building block for zero-knowledge arguments of membership and non-membership, where an argument of membership or non-membership allows to prove a committed value belongs or does not belong to a public set of values. 

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IEEE Transactions on Cloud Computing 2022 (IEEE TCC22)

Lingjuan Lyu, Sid Chi-Kin Chau, Nan Wang, Yifeng Zheng

We propose a multi-party computation protocol based on Paillier threshold cryptosystem. Our protocol enables privacy-preserving collaborative consumption in a semi-honest setting. 

Paper 

The 12th ACM International Conference on Future Energy Systems (ACM e-Energy 2021)

Nan Wang, Sid Chi-Kin Chau, Yue Zhou

We propose an efficient multi-party computation protocol and a blockchain-based cost-sharing solution to achieve energy storage sharing in a privacy-preserving manner. Our protocol leverages SPDZ framework to defend against a dishonest majority, who arbitrarily deviate from the protocol.

Paper 

Nan Wang#, Sid Chi-Kin Chau

We propose an efficient multi-party computation protocol to compute ranked-based statistics, e.g., median, percentiles, over distributed datasets. Our protocol achieves higher accuracy and stronger security compared with the state-of-the-art. Moreover, we leverage different zero-knowledge proofs to defend against malicious parties from dishonestly deviating from the protocol.

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