Digital evidence processing can be more critical in the heterogeneous Internet-of-Things (IoT) paradigm due to the lack of transparency, trust, integrity, and immutability. Researchers have conducted a substantial range of research over the past few decades to improve the digital chain of custody and forensic investigation. In a digital forensic investigation, preserving the digital evidence chain of custody with end-to-end security, integrity, privacy, traceability, access control, provenance, transparency, and evidence verification presents several challenges. The present paper proposes a blockchain-based model for a smart IoT environment to address these challenges. The primary goal of this study is to ensure the integrity, confidentiality, trust, and privacy of vital digital evidence throughout the forensic investigation. We only insert or delete digital evidence after verifying the user's authentication. We have utilized a consortium blockchain-based secure system that harnesses the benefits of an interplanetary file system (IPFS) to enhance the security and integrity of digital evidence management and chain-of-custody. The proposed mechanism can achieve security, integrity, access control, immutability, and trust for a digital chain-of-custody. The integration of the Ethereum blockchain-based test network and IPFS facilitates the development, testing, and deployment of decentralized applications (dApps) with enhanced security, efficiency, and decentralization. We deployed smart contracts on Metamask and tested them on the Sepolia test network. The Ethereum network records different gas fees and transaction fees based on various timestamps, gas prices, and traffic. In different numbers and timestamps, gas prices vary between 2.50000001 Gwei and 13.559962651 Gwei. Compared to many other transactions, the reduction ranges from 10 to 20%. The proposed model provides the highest throughput, approximately 5% more transactions per second, as well as the lowest latency.
