IoTLogBlock: Recording Off-line Transactions of Low-Power IoT Devices Using a Blockchain

For any distributed system, and especially for the Internet of Things, recording interactions between devices is essential. At first glance, blockchains seem to be suitable for storing these interactions, as they allow multiple parties to share a distributed ledger. However, at a closer look, blockchains require heavy computations, large memory capacity, and always-on communication to the cloud; these are three properties that are challenging for IoT devices with limited resources.In this paper, we present IoTLogBlock to address these challenges. IoTLogBlock connects resource-constrained IoT devices to the blockchain, and it consists of three building blocks jointly enabling recording transactions: a lightweight contract signing protocol, a blockchain network, and a smart contract. The contract signing protocol allows devices to interact locally to perform transactions, even if no communication to the cloud and the blockchain exists at that moment. At a later time, devices forward the stored transactions to the blockchain, where a smart contract ultimately verifies the transactions.We evaluate our design on low-power devices and quantify the performance in terms of memory, computation, and energy consumption. Our results show that a constrained device can create and sign a transaction within 3 s on average. Finally, we expose the devices to network scenarios with edge connections ranging from 10 s to over 2 h.