Phd Position F/m Byzantine Fault Tolerance and

Le descriptif de l’offre ci-dessous est en Anglais_

**Type de contrat **:CDD

**Niveau de diplôme exigé **:Bac + 5 ou équivalent

**Fonction **:Doctorant

**A propos du centre ou de la direction fonctionnelle**:
The Inria Rennes - Bretagne Atlantique Centre is one of Inria's eight centres and has more than thirty research teams. The Inria Center is a major and recognized player in the field of digital sciences. It is at the heart of a rich R&D and innovation ecosystem: highly innovative PMEs, large industrial groups, competitiveness clusters, research and higher education players, laboratories of excellence, technological research institute, etc.

**Contexte et atouts du poste**:
This PhD thesis will be in the context of a collaboration between HIVE and Wide and Coast Inria teams. The Ph.D student will be located at Inria Center of the University of Rennes and will be visiting team Coast at Inria Nancy-Grand Est and the Hive offices in Cannes.

About Hive:
Hive intends to play the role of a next generation cloud provider in the context of Web 3.0. Hive aims to exploit the unused capacity of computers to offer the general public a greener and more sovereign alternative to the existing clouds where the true power lies in the hands of the users. It relies both on distributed peer-to-peer networks, on the encryption of end-to-end data and on blockchain technology.

About Inria Center of the University of Rennes:
The Inria Center of the University of Rennes is one of Inria's eight centers and has more than thirty research teams. The Inria Center is a major and recognized player in the field of digital sciences. It is at the heart of a rich R&D and innovation ecosystem: highly innovative PMEs, large industrial groups, competitiveness clusters, research and higher education players, laboratories of excellence, technological research institutes, etc.

About Inria Nancy - Grand Est:
The Inria Nancy - Grand Est center is one of Inria's eight centers and has twenty project teams, located in Nancy, Strasbourg and Saarbrücken. Its activities occupy over 400 people, scientists and research and innovation support staff, including 45 different nationalities. The Inria Center is a major and recognized player in the field of digital sciences. It is at the heart of a rich R&D and innovation ecosystem: highly innovative PMEs, large industrial groups, competitiveness clusters, research and higher education players, laboratories of excellence, technological research institutes, etc.

**Mission confiée**:
A key challenge in a distributed storage system lies is withstanding the behavior of Byzantine nodes. These can result from malicious actors or simply from bugs or hardware problems, but in all cases they can render the system unusable in the absence of proper protocols [1]. Research in distributed algorithms has led to a number of protocols for managing Byzantine behavior in a classical, permissioned, setting [2, 3, 4, 5]. Yet operation in open permissionless settings remains challenging [6]. Currently, used methods like Proof-of-Work or Proof-of-Stake each have their own limitations. PoW suffers from enormous energy consumption, while PoS relies on the presence of a cryptocurrency or other similar asset.

In this PhD thesis, we plan to explore novel techniques to handle Sybil [10, 11, 12] and Byzantine attacks in the context of distributed storage. We will explore distributed storage solutions that, while not requiring the presence of a classical blockchain, can offer the same or even stronger guarantees in terms of fault-tolerance, data persistence, privacy, and security.

**Principales activités**:
Programme

The Ph.D. will consider this research question in two different contexts, close and open systems. These two context represents a gradation in the algorithmic and implementation difficulty of trustless distributed storage.

- In a first stage we will investigate large-scale trustless decentralized storage under a closed model. This model assumes that an attacker may comprise existing participants, but exclude attacks that require the injection of large numbers of new nodes, or the creation of novel identities. In this context the Ph.D. will consider the design, implementation and characterization of increasingly complex data-structures.

We will first consider append-only data structures, possibly with commutative operations. This type of storage object can be implemented using FIFO Byzantine Reliable Broadcast only [13]. Introduced in the eighties [14, 15], Byzantine reliable broadcast (BRB) is a fundamental abstraction of distributed computing [16, 17, 2, 18, 3, 4, 19, 20, 21]. BRB assumes that one particular process, the sender, broadcasts a message to the rest of the system, and that correct (a.k.a. honest) processes all deliver the value initially broadcast if the sender is correct, or that, if it is not, either all agree on some value, or that none delivers any value.

BRB algorithms are lighter and comput