Scalable Blockchain-Based Electronic Evidence Sharing Using HotStuffle Consensus and Zero-Knowledge Proofs

Abstract

Preservation and secure treatment of digital evidence across different courts of justice are serious issues due to trust, information leakage, scalability and dynamism. Existing centralised and blockchain-based evidence databases are vulnerable to single points of failure, are privacy-unfriendly, or have significant performance gaps at scale. To overcome these defects, this paper proposes a blockchain-based privacy-preserving and scalable electronic evidence management system for the judicial alliance environments. The proposed system will be constructed based on a consortium blockchain architecture, with HotStuffle Byzantine Fault Tolerant (BFT) consensus protocol, Zero-Knowledge Proof (ZKP) based access authorization, and a more operational Ciphertext-Policy Attribute-Based Encryption (CP-ABE) architecture. It is an on-chain/off-chain storage structure where cryptographic hash values, metadata, and access logs are stored on-chain to provide integrity, auditability, and non-repudiation. Conversely, encrypted electronic evidence files are not kept on blockchains to reduce storage overheads. ZKP supports privacy-sensitive authentication without disclosing valuable identity or role information, and the improved CP-ABE protocol supports finely grained, revocable access control by storing access policies in ciphertext. This has been supported by extensive testing through large-scale experimentation to demonstrate the effectiveness and practicability of the proposed framework. Scalability: The results show that end-to-end access latency increases by 240-910 ms as the number of validator nodes increases, confirming HotStuffle's consensus' scalability advantage. The system's throughput is almost linearly related to the rate of transaction arrivals, reaching a peak of 390 transactions/second, after which it starts levelling off. The overhead of ZKP during verification is low, and verification time increases by 36 ms and 8 ms for proofs of 10 KB and 80 KB, respectively. In addition, the time required to decrypt CP-ABE increases gradually with the number of access attributes, ranging from 5 to 285 ms. Conversely, even when 40 per cent of users are revoked, the revocation processing time remains reasonable. Security and comparative analysis demonstrate that the described framework can provide better privacy protection and fine-grained access control, resist collusion and replay attacks, and is more advantageous than existing blockchain-based models of electronic evidence sharing. Overall, the proposed system offers adequate scalability, privacy, and security; thus, it can be used for large-scale deployment of judicial alliances.