Paper 2023/1185

SwiftRange: A Short and Efficient Zero-Knowledge Range Argument For Confidential Transactions and More

Abstract

Zero-knowledge range proofs play a critical role in confidential transactions (CT) on blockchain systems. They are used to prove the non-negativity of committed transaction payments without disclosing the exact values. Logarithmic-sized range proofs with transparent setups, e.g., Bulletproofs, which aim to prove a committed value lies in the range $[0, 2^N-1]$ where $N$ is the bit length of the range, have gained growing popularity for communication-critical blockchain systems as they increase scalability by allowing a block to accommodate more transactions. In this paper, we propose SwiftRange, a new type of logarithmic-sized zero-knowledge range argument with a transparent setup in the discrete logarithm setting. Our argument can be a drop-in replacement for range proofs in blockchain-based confidential transactions. Compared with Bulletproofs, our argument has higher computational efficiency and lower round complexity while incurring comparable communication overheads for CT-friendly ranges, where $N \in \{32,64\}$. Specifically, a single SwiftRange achieves 1.73$\times$ and 1.37$\times$ proving efficiency with no more than 1.1$\times$ communication costs for both ranges, respectively. More importantly, our argument is doubly efficient in verification efficiency. Furthermore, our argument has a smaller size when $N \leq 16$, making it competitive for many other communication-critical applications. Our argument supports the aggregation of multiple single arguments for greater efficiency in communication and verification. Finally, we benchmarked our argument against the state-of-the-art range proofs to demonstrate its practicality.