TAR - PCH: Traceable and Revocable Blockchain Rewriting via Partial Policy-Hiding Chameleon Hashing under Cloud Assistance

Lifeng Guo, Jingjing Xie, Runtao Zhang, Wei-Chuen Yau

Abstract: The immutability of blockchain, while essential for ensuring data integrity and traceability, presents challenges in scenarios requiring data modification, such as regulatory compliance with the General Data Protection Regulation (GDPR) and correction of erroneous transactions. To address this, we propose TAR−PCH, a novel chameleon hash scheme that enables fine-grained, policy-controlled rewriting of blockchain data under cloud-assisted environments. Our construction extends the Policy-Based Chameleon Hash (PCH) framework by incorporating partial policy hiding, user-level and attribute-level revocation, and traceability of malicious users. Leveraging efficient attribute-based encryption and white-box tracing, TAR−PCH enforces strong access control and accountability while outsourcing costly operations to the cloud. We formalize its security via indistinguishability and collision-resistance models, and our implementation demonstrates practical performance and scalability compared to existing schemes.

External IDs:dblp:conf/trustcom/GuoXZY25