Vers une arithmétique efficace pour le chiffrement homomorphe basé sur le Ring-LWE

Fully homomorphic encryption is a kind of encryption offering the ability to manipulate encrypted data directly through their ciphertexts. In this way it is possible to process sensitive data without having to decrypt them beforehand, ensuring therefore the datas' confidentiality. At the numeric and cloud computing era this kind of encryption has the potential to considerably enhance privacy protection. However, because of its recent discovery by Gentry in 2009, we do not have enough hindsight about it yet. Therefore several uncertainties remain, in particular concerning its security and efficiency in practice, and should be clarified before an eventual widespread use. This thesis deals with this issue and focus on performance enhancement of this kind of encryption in practice. In this perspective we have been interested in the optimization of the arithmetic used by these schemes, either the arithmetic underlying the Ring Learning With Errors problem on which the security of these schemes is based on, or the arithmetic specific to the computations required by the procedures of some of these schemes. We have also considered the optimization of the computations required by some specific applications of homomorphic encryption, and in particular for the classification of private data, and we propose methods and innovative technics in order to perform these computations efficiently. We illustrate the efficiency of our different methods through different software implementations and comparisons to the related art.Le chiffrement totalement homomorphe est un type de chiffrement qui permet de manipuler directement des données chiffrées. De cette manière, il est possible de traiter des données sensibles sans avoir à les déchiffrer au préalable, permettant ainsi de préserver la confidentialité des données traitées. À l'époque du numérique à outrance et du "cloud computing" ce genre de chiffrement a le potentiel pour impacter considérablement la protection de la vie privée. Cependant, du fait de sa découverte récente par Gentry en 2009, nous manquons encore de recul à son propos. C'est pourquoi de nombreuses incertitudes demeurent, notamment concernant sa sécurité et son efficacité en pratique, et devront être éclaircies avant une éventuelle utilisation à large échelle.Cette thèse s'inscrit dans cette problématique et se concentre sur l'amélioration des performances de ce genre de chiffrement en pratique. Pour cela nous nous sommes intéressés à l'optimisation de l'arithmétique utilisée par ces schémas, qu'elle soit sous-jacente au problème du "Ring-Learning With Errors" sur lequel la sécurité des schémas considérés est basée, ou bien spécifique aux procédures de calculs requises par certains de ces schémas. Nous considérons également l'optimisation des calculs nécessaires à certaines applications possibles du chiffrement homomorphe, et en particulier la classification de données privées, de sorte à proposer des techniques de calculs innovantes ainsi que des méthodes pour effectuer ces calculs de manière efficace. L'efficacité de nos différentes méthodes est illustrée à travers des implémentations logicielles et des comparaisons aux techniques de l'état de l'art

Extra back-off flow control in wireless mesh networks Ton Hellings

Abstract—CSMA is the predominant distributed access protocol for wireless mesh networks. Originally designed for singlehop settings, in multi-hop networks CSMA can exhibit severe performance problems in terms of stability and end-to-end throughput. To ensure a smoother flow of packets, we examine a new scheme referred to as extra back-off (EB) flow control. In this scheme a node remains silent for a certain extra back-off time (imposed on top of the usual back-off time that is part of CSMA) after it has transmitted a packet, so as to give both the downstream and upstream neighbors the opportunity to transmit. EB flow control entails only a small modification to CSMA, preserving its distributed character, yet considerably improving the network performance. I

Termination of Simply Moded Logic Programs with Dynamic Scheduling

In logic programming, dynamic scheduling indicates the feature by means of which the choice of the atom to be selected at each resolution step is done at runtime and does not follow a fixed selection rule such as the left-to-right one of Prolog. Input consuming derivations were introduced to model dynamic scheduling while abstracting from the technical details. In this article, we provide a sufficient and necessary criterion for termination of input consuming derivations of simply moded logic programs. The termination criterion we propose is based on a denotational semantics for partial derivations which is defined in the spirit of model-theoretic semantics previously proposed for left-to-right derivations

Talk of Europe - The debates of the European Parliament as Linked Open Data

--- Please note: this dataset is replaced by a new version. A link to the new version is provided under 'Relation'. --- The Talk of Europe (TOE) project has curated the proceedings of the European Parliament (EP) from 1999 onwards, including all available translations in other EU languages, and converted these to RDF. Moreover, the data are enriched with biographical and political information on the speakers. Since the data are available in multilingual form, this dataset lends itself to be linked with resources in other European countries, such as parliamentary records or news reports

Searchable Encryption Revisited: Consistency Properties, Relation to Anonymous IBE, and Extensions

We identify and fill some gaps with regard to consistency (the extent to which false positives are produced) for public-key encryption with keyword search (PEKS). We define computational and statistical relaxations of the existing notion of perfect consistency, show that the scheme of [8] is computationally consistent, and provide a new scheme that is statistically consistent. We also provide a transform of an anonymous identity-based encryption (IBE) scheme to a secure PEKS scheme that, unlike the previous one, guarantees consistency. Finally, we suggest three extensions of the basic notions considered here, namely anonymous hierarchical identity-based encryption

Talk of Europe - The debates of the European Parliament as Linked Open Data

The Talk of Europe (TOE) project has created a Linked Open Dataset with data from and about the European Parliament (EP). The proceedings of the parliamentary debates as published by the EP, including all available translations, were converted to RDF and enriched with datasets of biographical and political information about the speakers. The ToE project officially ran from from 2014 to 2015 and has continued to make improved and updated versions of the data available online. The current dataset that is archived here contains all debates from summer 1999 until summer 2017. The dataset is documented in a publication: Astrid van Aggelen, Laura Hollink, Max Kemman, Martijn Kleppe, Henri Beunders. The debates of the European Parliament as Linked Open Data. Semantic Web, vol. 8, no. 2, pp. 271-281, 2017, IOS Press. A pre-print is added to this dataset as onderzoeksdocumentatie_preprint.pdf. This pre-print relates to the previous version of this dataset. Changes to the dataset with respect to the descrition in the publication are listed in the file Changes.txt