Enabling secure lightweight mobile Narrowband Internet of Things (NB-IoT) applications using blockchain.

Narrowband Internet of Things (NB-IoT) is a low bandwidth 3GPP communication standard transmitting small quantities of data over long distances at random intervals. However, as NB-IoT cannot support seamless handover between base stations, its applications are limited to stationary devices, which may result in the potential risk of fake base station connections in an attempt to maintain connectivity across cells. Considering characteristics such as low power consumption and high connection density, researchers envision using NB-IoT in mobile applications such as public-bike sharing, pet tracking etc. Connecting NB-IoT devices using decentralised architecture such as blockchain ensures seamless communication in mobile applications and eliminates bottlenecks due to multiple data requests observed in centralised networks. In this paper, we develop a hybrid blockchain framework facilitating mutual authentication between base stations to enhance user privacy and prevent fake base station connections and certificate transfers. Zero-knowledge proof used as the consensus algorithm enhances user privacy and message confidentiality. IoT devices are designed to store the hashes of their approved transactions as a linear hash chain instead of the complete merkle tree to minimise hash verification complexity. Additionally, base station memory is partitioned dynamically to enhance scalability and memory utilisation efficiency. We prototype our framework on Remix IDE in Ethereum and implement it on Raspberry Pi 4. The security of the proposed framework is formally verified using Scyther. Further, we show that our approach achieves 80.50% lower computational power, 74.73% lower execution time and 50% lower memory, respectively, in comparison with existing schemes making our proposed scheme lightweight.