CAREER: Scalable Consensus Protocol Design with Accountability and Privacy under Practical Failure Models

In many fields, such as commerce and finance, a small number of organizations are trusted to maintain the integrity of data and transactions. If these organizations fail, the core integrity property is lost. Blockchains systems form the critical infrastructure and technology for decentralizing trust to multiple parties such that integrity is maintained even if some of them are malicious. Due to the value of the information stored, these systems need the ability to tolerate a significant fraction of malicious parties, ensure these parties do not have an incentive to misbehave, and hold parties accountable and recover in case of an attack. Moreover, for scalability, these systems need to have low communication complexity, good latency, and support private transactions. Unfortunately, existing blockchain systems do not meet all of these requirements. This project makes novel scientific advances by bridging the gap between theoretical foundations and the practical aspects of blockchain consensus by considering several properties such as accountability, practical failure models, and privacy. The project's broader significance and importance include: (i) improved designs for public blockchains such as Ethereum and Zcash, industry-based permissioned blockchains such as VMware Concord, and applications such as decentralized finance and Central Banking Digital Currencies, (ii) a comprehensive education, dissemination, and outreach plan resulting in (a) new graduate and undergraduate courses with open-source materials, (b) the mentoring of graduate, undergraduate, and high school students, and (c) organizing events that facilitate interdisciplinary collaboration on blockchains. The project exploits and reveals synergies between distributed computing, theory, privacy, game theory, and computer systems. It answers fundamental research questions on 1) defining and studying mechanisms for fault detection and recovery and how they act as a feedback loop to the security and efficiency of the system, 2) designing secure and efficient self-stabilizing synchronous protocols tolerating minority corruption, 3) analyzing consensus in the presence of rational parties, and 4) understanding the limits of and designing randomized privacy mechanisms for privacy-preserving proof-of-stake protocols. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.