Fairledger: a Fair Proof-of-Sequential-Work based Lightweight Distributed Ledger for IoT Networks

Blockchain has been recognized as a promising solution to construct a tamper-proof and trust-free decentralized framework for Internet of Things (IoT) systems. However, directly applying cryptocurrency-oriented blockchains in IoT networks still meets tremendous limitations. Proof-of-Work (PoW) consensus protocol enables a blockchain to achieve pseudonymity, scalability and probabilistic finality in an asynchronous and open-access network environment. The compute-intensive PoW favors nodes possessing more computing power, but fairness is an important requirement in highly heterogeneous IoT networks. A blockchain designed for IoT edge environments must consider devices with various constraints on computation power. This paper proposes Fair-ledger, a fair Proof-of-Sequential-Work (PoSW) based lightweight distributed ledger for small-scale, permissioned IoT networks. By combining efficient verifiable delay function (eVDF) and Proofof-Credit (PoC) puzzle, PoSW consensus protocol guarantees fairness by requiring all the miners perform a fixed sequential computing steps to represent PoW for block generation despite their hardware resources. Due to the virtual milling manner of PoSW, Fairledger demonstrates computing efficiency compared to traditional PoW blockchains. In addition, Fairledger is less susceptible to "long-range" and "nothing-at-stake" attacks than Proof-of-Stake (PoS) protocols are. A proof-of-concept prototype is implemented, and the experimental results verify the feasibility of running Fairledger in a physical IoT network with higher throughput, less computation and communication cost, and better security guarantees.