Enforcing the Security and Usability of Blockchain for a Smart City Cyberinfrastructure

The development of smart cyberinfrastructures on the basis of the Internet of Things has caused the penetration of new technologies into the spheres of unmanned transportation, robotic buildings, and digital economy, and then, as a result of the integration of cyber-physical systems with monitoring, analytical, and control means, a new intelligent urban paradigm of a ‘smart city’. Noting the high criticality of this system, specific threats are aimed at disrupting its connectivity, resource capturing, functional availability, data privacy, and safety. As a protective measure, blockchain is a usual part of the security arsenal of any distributed system, providing provable security to all its participants. However, in a large-scale smart city's cyberinfrastructure, blockchain itself becomes a target of specific cyber threats, e.g., a ‘51% attack’. Also, the blockchain's usability issue is the unlimited growth of its structure, leading to exhaustion of free resources and thus depressing its use. Conventional approaches to preventing the blockchain from these issues downgrades its scalability and therefore are not widely applicable in a smart city. This paper proposes a new technique to protect the blockchain applied in a large-scale smart city network infrastructure. The proposed solution combines assessing the intruder's capabilities and providing dynamic adaptation of the blockchain to evolving threats. To avoid infinite growth of the blockchain, the blockchain with a floating genesis block and fixing blocks has been implemented. The developed modifications retain the ability to scale the blockchain. The experimental study has demonstrated the effectiveness of the proposed approach.