Two-tier reputation-based blockchain architecture against false data injection in smart AMI systems

False Data Injection Attack (FDIA) represents one of the major cyber attacks against smart Advanced Metering Infrastructure (AMI) systems, as it involves injecting fabricated data into the AMI system, which could cause significant physical and economic losses for utilities and consumers. In this paper, we propose a two-tier reputation-based blockchain framework to protect data measurements from FDIA. The framework consists of two main blockchains: (1) Neighbor Area Network (NAN) blockchain, which aims to ensure the integrity of measurements that are transmitted from the smart meters to the data concentrators, and (2) Wide Area Network (WAN) blockchain, which aims to protect the measurements that are transmitted from the concentrators to the control center of the utility. The blockchains operate on a consensus protocol named PoR-BFT, which combines a proposed Proof-of-Reputation (PoR) consensus and Practical Byzantine fault tolerance (PBFT) consensus. This combination enables the evaluation of node behavior and the detection of malicious nodes in the network. We analyze and evaluate the security and scalability of the proposed framework and compare it to two state-of-the-art solutions, named One-BC and WAN-BC. The comparison shows that our framework incurs the lowest successful attack probability, and it is the closest competitor to WAN-BC in terms of scalability. By applying the Pareto optimal front algorithm, our framework ensures the best trade-off between scalability and security. We also use HyperLedger Fabric platform to demonstrate the effectiveness of PoR-BFT consensus compared to PBFT in terms of latency and detection rate of malicious nodes.