Design and Implementation of a Privacy-Preserving Revocable Credential System Based on Blockchain Technology

Abstract

Existing blockchain credential systems still face two coupled problems: transparent on-chain data may disclose holder privacy, while immutable records make invalid credentials difficult to revoke. This paper implements a privacy-preserving revocable credential system in an EVM-compatible simulated blockchain environment. The main innovations are threefold: first, a blockchain–IPFS hybrid architecture stores credential details off-chain and anchors only hCID, Merkle roots, and anonymous revocation nullifiers on-chain; second, a zk-SNARK and Merkle accumulator prove credential validity without revealing holder identity, credential identifiers, or credential contents; third, a dual-role institution–regulator revocation mechanism changes credential status through pending and confirmed states, reducing single-role authority abuse. Experiments on a repeatable Hardhat-based simulated network show that the system completes the full workflow of issuance, privacy-preserving verification, and revocation. Single proof generation averages 0.72 s, and end-to-end verification latency is 0.78 s, 0.96 s, 1.46 s, and 2.24 s under 1, 10, 50, and 100 concurrent users, respectively. The revocation confirmation transaction consumes 48,500 gas, 25.4% lower than the single-admin baseline, while the full two-step revocation workflow consumes 93,620 gas. Mythril and Slither audits detect no high-risk vulnerabilities.