Enhancing Efficiency and Fine-Grained Control in Redactable Blockchains with EPBCHF

Blockchain technology has presented a promising decentralized paradigm to preclude trusted third parties' dominancy. It is a transparent and distributed ledger initially designed for digital cryptocurrencies while currently extended to serve various industries. However, Blockchain immutability presents challenges, as it can be misused for storing illicit content, violating privacy regulations, and limiting data management flexibility. Policy Based Chameleon Hash Function (PBCH) has transformed blockchain rewriting contents concept via permitting modifiers to amend certain transaction since they possessed fundamental privileges satisfying certain access policy. However, PBCHF suffers from efficiency issues due to its reliance on Chameleon Hash ephemeral Trapdoor (CHET) and Attribute-Based Encryption (ABE), significantly impacting overall efficiency. We propose the Efficient Policy-Based Chameleon (EPBCHF) construction by replacing CHET with Chameleon-Hashes by Dual Long-Term Trapdoors (CHDLTT) to address these challenges. Additionally, we introduce an enhanced encryption scheme resilient against chosen-ciphertext attacks (CCA) without compromising overall efficiency. Modelling EPBCHF proves practical instantiation accompanied by rigorous security proofs. Our construction provides a fine-grained redactable blockchain in comparison to the currently proposed solutions. The evaluated results confirm that the proposed EPBCHF is scalable and efficient due to having the ability to handle unlimited transaction volumes additionally, data is efficiently processed without further overhead meanwhile data size consistency reflects a robust memory management due to predicted memory size, network bandwidth and storage requirement for future growth thereby, EPBCHF is proven to be reliable and scalable. © 2024 College of Education, Al-Iraqia University. All rights reserved.