Talk de Pierre-Louis Roman

Abstract:
The rise of cryptocurrencies took the academic community by surprise by introducing a new paradigm for distributed computing.  Cryptocurrencies operate in a novel model of permissionless membership whereby anyone may join the system without prior permission to do so from any authority. As such, permissionless systems can securely access a seemingly infinite amount of untrusted resources on the Internet.  This permissionless model stands at the very opposite of what has been at the core of distributed computing research for decades: a permissioned model that requires explicit permission in order to join a system.

However, permissionless systems are not a panacea.  They typically require costly mechanisms to operate and are based on little theoretical foundations which often renders them less secure and efficient than planned.  On the other hand, permissioned systems have the significant benefit of having been refined over decades of research in secure distributed computing, also known as Byzantine computing.  We believe that systems bringing the best of both worlds can be achieved.

In this talk, we review a recent line of work that conceptualizes and explores the efficiency of a hybrid model that bridges the permissioned and permissionless ones.  To do so, we integrate brokers, that embody permissionless and untrusted resources, into a classic permissioned model.  The task of brokers is simple: accelerate the permissioned system in order to reach levels of performances unachievable by a fully permissioned system.  More specifically, this talk describes how brokers can be integrated into (1) a reliable broadcast protocol, that is necessary and sufficient to replicate a payment system, and (2) a total order broadcast protocol, that is able to replicate any service.

Biography :
Pierre-Louis Roman is a postdoc in the Distributed Computing Lab led by Rachid Guerraoui at EPFL. He mostly works on the security and efficiency of the systems powering cryptocurrencies such as blockchains and distributed ledgers. He is also interested in hardware/software co-designs for data center systems.
Pierre-Louis was previously working on secure and efficient data center systems as a postdoc with Patrick Eugster at USI Lugano. He completed his PhD on decentralized systems in 2018 supervised by François Taïani and Davide Frey at the University of Rennes and by Spyros Voulgaris at VU Amsterdam during a summer visit. Earlier, he received an MSc in 2013 and a BSc in 2011 both in computer science from Sorbonne University.