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

Abstract

 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 PolicyBased 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.