Secure Blockchains For Cyber Physical Systems

"Blockchains are a data structure used to perform state agreement in a distributed system across an entire network. One unique trait of blockchains is the lack of a centralized trusted third-party to control the system. This prevents a corrupted trusted third party from being able to control the entire blockchain. All nodes can reach agreement in an untrusted network where nodes do not need to trust one another to believe the accuracy of the information stored. Two main issues occur when trying to apply this technology to other applications: verifiability and scalability. In previous blockchain architectures, there is no way to validate off-chain data i.e. sensor reading. Some have purposed the use of a trusted third-party. Unfortunately, using a trusted third-party undoes a main advantage of blockchains and allows corruption to become a concerning possibility. Other challenges to applying blockchains to cyber-physical systems include keeping a single ledger up-to-date in real-time. The drawbacks of Bitcoin, a popular application of blockchains, have been very well documented in terms of speed. The main purpose of this work is to address the verifiability and scalability issues of blockchains for cyber-physical systems. It proposes a solution that expands the application of blockchains to cyber-physical systems while maintaining the benefits. If the use of blockchains is to be expanded to off-chain data, they need to have the capability to securely encapsulate the physical world in a verifiable way. The following is a list of major contributions by the work: 1) propose a framework for verifying physical transactions in a blockchain, 2) propose a method to increase scalability and allow the use of blockchains in a disconnected network, 3) propose a truncation mechanism for cyber-physical transactions that allow for real-time speed. With these three contributions, this work introduces some additional ideas to blockchains and expands their applications"--Abstract, page iii.