LEChain: A blockchain-based lawful evidence management scheme for digital forensics

Lawful evidence management in digital forensics is of paramount importance in police investigations because such evidence is used to convict suspects of crimes. Existing studies have adopted cloud computing to collect evidence and then leveraged blockchain to support the transparency, immutability, and auditability of the evidence. Unfortunately, such studies only rely on a weak security model and do not cover the entire life cycle of the evidence or address the key privacy issues, i.e., witness privacy in evidence collection and juror privacy in court trials. In this work, we propose LEChain, a blockchain-based lawful evidence management scheme to supervise the entire evidence flow and all of the court data (e.g., votes and trial results), extending from evidence collection and access during the police investigation to jury voting in the court trials. Specifically, we utilize short randomizable signatures to anonymously authenticate witnesses’ identities to protect the witness privacy. Then, we leverage fine-grained access control based on ciphertext-policy attribute-based encryption for evidence access. Next, we design a secure voting method to protect juror privacy. In addition, we build a consortium blockchain to record evidence transactions. Finally, we formally analyze the security and privacy of LEChain and evaluate its computational costs and communication overhead by implementing a prototype based on a local Ethereum test network.