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Dissertation Defense - Golam Bashar

October 18, 2021 @ 1:00 pm MDT

Fair and Efficient Consensus Protocols for Secure Blockchain Applications


In blockchain technology, consensus protocols serve as mechanisms to reach agreements among a distributed network of nodes. In this work, we propose three novel protocols for permissioned, healthcare, and supply chain blockchain.

(1) Proof of Queue (PoQ), for private blockchains, combines the lottery strategy of PoET with a specialized round-robin algorithm where each node has an equal chance to become a leader with equal access. PoQ is relatively scalable without any collision. Like PoET, PoQ uses Intel SGX, a Trusted Execution Environment, to generate a secure random waiting time to choose a leader and fairly distribute the leadership role to everyone on the network. Our analysis and experiments show that PoQ provides significant performance improvements over PoET, and its fairness scales linearly with the number of SGX nodes in the network.

(2) ACCORD, a quorum-based multi-leader protocol for health record management that achieves fork-resistance, robustness, and scalability. ACCORD consists of three distinct components: (a) an asynchronous quorum selection procedure to designate the creators of future blocks, (b) a block creation protocol run by the quorum to prevent omissions in the presence of honest quorum members, and (c) a decentralized arbitration protocol to ensure consensus by voting. We define the threat model and perform security analysis on the protocol. We also implemented the protocol and conducted experiments to demonstrate effectiveness of the protocol.

(3) In response to the Drug Supply Chain Security Act (DSCSA), we introduce Janus, a novel pharmaceutical track-and-trace system that utilizes blockchain and cloning-resistant hologram tags to prevent counterfeits from entering the pharmaceutical supply chain. We designed a multi-quorum consensus protocol that achieves load balancing across the network. We perform a security analysis to show robustness against various threats and attacks. We implemented Janus, and the experimental results show that the system is fair, scalable, and resilient.



Dr. Gaby Dagher (Chair), Dr. Nader Rafla, Dr. Jidong Xiao