BlockSDN: Blockchain-as-a-Service for Software Defined Networking in Smart City Applications

Smart cities have emerged as a hub of intelligent applications (e.g., intelligent transportation systems, smart parking, smart homes, and e-healthcare) to provide ambient-assisted living and quality of experience to wide communities of users. The smooth execution of these applications depends on reliable data transmission between various smart devices and machines. However, the exponential increase in data traffic due to the growing dependency of end users on smart city applications has created various bottlenecks (e.g., channel congestion, manual flow configurations, limited scalability, and low flexibility) on the conventional network backbone, which can degrade the performance of any designed solution in this environment. To mitigate these challenges, SDN emerges as a powerful new technology that provides global visibility of the network by decoupling the control logic from the forwarding devices. The abstraction of network services in SDN architecture provides more flexibility for network administrators to execute various applications. In SDN architecture, the decision making process is handled by a logically centralized controller, which may have a single point of failure. An adversary/ attacker can compromise the controller using different types of attacks (e.g., eavesdropping, man-in-the middle attack, and distributed denial of service) in order to gain total control of the network by updating the flow table entries at the data plane or hindering control plane operations. Therefore, to cope with the aforementioned challenges, new strategies and solutions are required for securing the SDN-enabled network architecture at different planes and their associated interconnections. In this article, various security issues and different attack vectors are discussed along with possible solutions. To mitigate various attacks, BlockSDN, a blockchain as a service framework, for SDN is proposed. The architecture of permissioned blockchain is presented followed by two attack scenarios, 1) a malware compromised switch at the data plane and 2) distributed denial of service attack at the control plane, to demonstrate the applicability of the BlockSDN framework for various future applications. Finally, the open issues and challenges with respect to the design of blockchain solutions for SDN in smart city applications are also discussed.