Formalizing and Implementing Distributed Ledgers: A Distributed Computing Point of View
Speaker Chryssis Georgiou, University of Cyprus
Despite the hype about blockchains and distributed ledgers, no formal abstraction of these objects has been proposed. In this talk, I will overview a formulation of a distributed ledger object that together with collaborators have recently proposed. This formalization is influenced by the decades of research in the Distributed Computing community on formalizing distributed objects. In brief, we define a ledger object as a sequence of records, and we provide the operations and the properties that such an object should support. Implementation of a ledger object on top of multiple (possibly geographically dispersed) computing devices gives rise to the distributed ledger object. In contrast to the centralized object, distribution allows operations to be applied concurrently on the ledger, introducing challenges on the consistency of the ledger in each participant. We provide the definitions of three well-known consistency guarantees in terms of the operations supported by the ledger object: (1) atomic consistency (linearizability), (2) sequential consistency, and (3) eventual consistency. We then provide implementations of distributed ledgers on asynchronous message passing crash-prone systems using an Atomic Broadcast service and show that they provide eventual, sequential or atomic consistency semantics. The talk will conclude with a discussion on a variation of the ledger "the validated ledger" which requires that each record in the ledger satisfies a particular validation rule, and mention possible future research directions.
The talk is based on work performed jointly with Antonio Fernandez Anta (IMDEA Networks Institute, Spain), Kishori Konwar (MIT, USA) and Nicolas Nicolaou (KIOS CoE, Cyprus).
Chryssis Georgiou is an Associate Professor in the Department of Computer Science at the University of Cyprus. He holds a Ph.D. (December 2003) and M.Sc. (May 2002) in Computer Science & Engineering from the University of Connecticut and a B.Sc. (June 1998) in Mathematics from the University of Cyprus. His research interests span the Theory and Practice of Fault-tolerant Distributed and Parallel Computing with a focus on Algorithms and Complexity. Specific topics include Distributed Cooperation, Distributed Storage, Information Dissemination and Algorithmic Game Theory. He has published more than 90 articles in journals and conference proceedings in his area of study and he has authored two books on Robust Distributed Cooperative Computing. He served on several Program Committees of conferences in Distributed and Parallel Computing and on the Steering Committees of DISC and PODC. In 2015 he served as the General Chair of PODC 2015, in 2017 he co-chaired the Self-Stabilization Track of SSS 2017, and in 2018 he co-chaired the workshop ApPLIED 2018 (the workshop was co-located with PODC 2018).
Analysen, meeting room,
19 September, 2018, 13:00
19 September, 2018, 14:00