Section: Application Domains

Cloud storage

The team is concerned with several aspect of reliability and security of cloud storage, obtained mainly with tools from coding theory. On the privacy side, we build protocols for so-called Private Information Retrieval which enable a user to query a remote database for an entry, while not revealing his query. For instance, a user could query a service for stock quotes without revealing with company he is interested in. On the availability side, we study protocols for proofs of retrievability, which enable a user to get assurance that a huge file is still available on a remote server, with a low bandwith protocol which does not require to download the whole file. For instance, in a peer-to-peer distributed storage system, where nodes could be rewarded for storing data, they can be audited with proof of retrievability protocols to make sure they indeed hold the data.

We investigate these problems with algebraic coding theory, mainly codes with locality (locally decodable codes, locally recoverable codes, and so on).

An M2 intern, Maxime Roméas, Bordeaux university, studied the constructive cryptography model, "A study of the Constructive Cryptography model of Maurer et. al." 5 months, followed by a PhD grant from IP Paris/Ecole Polytechnique for a 3-year doctorate (Oct 2019-Sept 2022): "The Constructive Cryptography paradigm applied to Interactive Cryptographic Proofs".

The Constructive Cryptography framework redefines basic cryptographic primitives and protocols starting from discrete systems of three types (resources, converters, and distinguishers). This not only permits to construct them effectively, but also lighten and sharpen their security proofs. One strength of this model is its composability. The purpose of the PhD is to apply this model to rephrase existing interactive cryptographic proofs so as to assert their genuine security, as well as to design new proofs. The main concern here is security and privacy in Distributed Storage settings.