# EconLedger: A Proof-of-ENF Consensus Based Lightweight Distributed Ledger for IoVT Networks
###### Abstract  
The rapid advancement in artificial intelligence (AI) and wide deployment of Internet of Video Things (IoVT) enable situation awareness (SAW). The robustness and security of IoVT systems are essential for a sustainable urban environment. While blockchain technology has shown great potential in enabling trust-free and decentralized security mechanisms, directly embedding cryptocurrency oriented blockchain schemes into resource-constrained Internet of Video Things (IoVT) networks at the edge is not feasible. By leveraging Electrical Network Frequency (ENF) signals extracted from multimedia recordings as region-of-recording proofs, this paper proposes EconLedger, an ENF-based consensus mechanism that enables secure and lightweight distributed ledgers for small-scale IoVT edge networks. The proposed consensus mechanism relies on a novel Proof-of-ENF algorithm where a validator is qualified to generate a new block if and only if a proper ENF-containing multimedia signal proof is produced within the current round. The decentralized database (DDB) is adopted in order to guarantee efficiency and resilience of raw ENF proofs on the off-chain storage. A proof-of-concept prototype is developed and tested in a physical IoVT network environment. The experimental results validated the feasibility of the proposed EconLedger to provide a trust-free and partially decentralized security infrastructure for IoVT edge networks. e +
Footnote †: journal: Future Internet  
society. The inherent security guarantees of blockchain lay down the foundations of serverless record keeping, without the need for centralizing trusted third-party authorities [4]. Blockchain runs on a decentralized peer-to-peer (P2P) network in order to securely store and verify data without relying on a centralized trust authority. The decentralization removes the risk of singular point of failures and mitigates bottleneck performances, which were inherent in centralized architectures. In addition, blockchain leverages distributed consensus protocols to enable a verifiable process for fault tolerance and tamper-proof storage on a public distributed ledger. Therefore, transparency, immutability, and auditability guaranteed by blockchain ensure resilience, correctness, and provenance for all data sharing among untrusted participants. Internet of Video Things (IoVT) provides a broad spectrum of applications, particularly in the area of public safety [5]. Migrating from centralized cloud-based paradigms to decentralized blockchain-based methods renders IoVT systems more efficient, scalable, and secure. However, directly integrating cryptocurrency-oriented blockchains into resource constrained IoVT systems is difficult in terms of handling the blockchain trilemma [6], which points out that decentralization, scalability, and security cannot perfectly co-exist. Most IoVT devices are highly resource constrained. Therefore, computing and storage intensive consensus protocols are not affordable, such as Proof-of-Work (PoW) [7], Proofs-of-Retrievability (PORs) [8], or Practical Byzantine Fault Tolerant (PBFT) [9], which come with high communication complexity and poor scalability. In addition, IoVT systems involve a large volume of real-time transactions. Higher throughput and lower latency become key metrics in blockchain-based systems for IoVT deployed on edge networks. Furthermore, DLTs are not general-purpose databases. The storage overhead is prohibitively high if raw data generated by IoVT transacting networks are stored in the blockchain. The Electrical Network Frequency (ENF) is the power supply frequency which fluctuates around its nominal frequency (50/60 Hz). The frequency fluctuations vary based on geographical region. The ENF fluctuations estimated from simultaneously recorded audio/video recordings within a power grid have a high correlation similarity [10].