1,720,961 research outputs found
RLWE-based distributed key generation and threshold decryption
Get PDFEver since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The most prominent field in post-quantum cryptography is lattice-based cryptography, protocols that are proved to be as difficult to break as certain difficult lattice problems like Learning With Errors (LWE) or Ring Learning With Errors (R-LWE). This Master s Degree Thesis forwards and elevates the work done in the Bachelor s Degree Thesis "Lattice-based Threshold Cryptography" by taking the R-LWE-based protocols specified there and giving more accurate and improved proofs of correctness and security, developing an original proposal for dispute resolution throughout both protocols, making an analysis of the specific hardness of breaking security of the protocol and analyzing a given implementation of both protocols in C
Lattice-based threshold cryptography
Get PDFEver since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The goal of this bachelor's degree thesis is to develop a post-quantum threshold cryptosystem, in particular based on Ring Learning with Errors, a lattice-based problem
Analyse Confidentielle de Données sur Bases de Données Chiffrées : Mélange de Chiffrement Fonctionnel et Confidentialité Différentielle Calculatoire
No full textIn our current digitalized society, data is ruling the world. But as it is most of the time related to individuals, its exploitation should respect the privacy of the latter. This issue has raised the differential privacy paradigm, which permits to protect individuals when querying databases containing data about them. But with the emergence of cloud computing, it is becoming increasingly necessary to also consider the confidentiality of "on-cloud'' storage confidentiality of such vast databases, using encryption techniques. This thesis studies how to provide both privacy and confidentiality of such outsourced databases by mixing two primitives: computational differential privacy and functional encryption. First, we study the relationship between computational differential privacy and functional encryption for randomized functions in a generic way. We analyze the privacy of the setting where a malicious analyst may access the encrypted data stored in a server, either by corrupting or breaching it, and prove that a secure randomized functional encryption scheme supporting the appropriate family of functions guarantees the computational differential privacy of the system. Second, we construct efficient randomized functional encryption schemes for certain useful families of functions, and we prove them secure in the standard model under well-known assumptions. The families of functions considered are linear functions, used for example in counting queries, histograms and linear regressions, and quadratic functions, used for example in quadratic regressions and hypothesis testing. The schemes built are then used together with the first result to construct encrypted databases for their corresponding family of queries. Finally, we implement both randomized functional encryption schemes to analyze their efficiency. This shows that our constructions are practical for databases with up to 1 000 000 entries in the case of linear queries and databases with up to 10 000 database entries in the case of quadratic queries.Dans l'actuelle société numérique, les données dominent le monde. Associées la plupart du temps à des individus, leur exploitation doit respecter la vie privée de ces derniers. Cette contrainte a donné naissance au paradigme de confidentialité différentielle, qui permet de protéger les individus lors de requêtes sur des bases contenant des données les concernant. Mais avec l'émergence du "cloud computing'', il devient nécessaire de prendre en compte la confidentialité du stockage de ces dernières dans le cloud, en utilisant du chiffrement. Cette thèse étudie comment assurer à la fois la confidentialité et le respect de la vie privée de ces bases de données externalisées en combinant deux primitives : la confidentialité différentielle calculatoire et le chiffrement fonctionnel. Dans un premier temps, nous étudions les liens entre la confidentialité différentielle calculatoire et le chiffrement fonctionnel pour des fonctions aléatoires d'un point de vue générique. Nous analysons la confidentialité dans un cadre où un analyste malicieux peut accéder aux données chiffrées stockés dans un serveur soit par corruption soit par brèche de sécurité, et nous prouvons qu'un schéma de chiffrement fonctionnel aléatoire sûr et pour la famille de fonctions appropriée garantie la confidentialité différentielle calculatoire du système. Dans second temps, nous construisons des schémas de chiffrement fonctionnel aléatoire pour certaines familles de fonctions utiles, et nous les prouvons sûrs dans le modèle standard sous des hypothèses très étudiées. Les familles de fonctions que nous étudions sont les fonctions linéaires, utilisées par exemple pour requêtes de comptage, des histogrammes et régressions linéaires, et les fonctions quadratiques, utilisées par exemple pour régressions quadratiques et tests d'hypothèses. Les schémas proposés sont utilisés avec le premier résultat pour construire des bases des données chiffrées pour fonctions linéaires et quadratiques respectivement. Finalement, nous implémentons les deux schémas de chiffrement fonctionnel pour analyser leur efficacité. Cela montre que nos constructions sont pratiques pour des bases de données avec 1 000 000 entrées pour des requêtes linéaires et des bases de données avec 10 000 entrées pour des requêtes quadratiques
Lattice-based threshold cryptography
Get PDFEver since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The goal of this bachelor's degree thesis is to develop a post-quantum threshold cryptosystem, in particular based on Ring Learning with Errors, a lattice-based problem
Analyse Confidentielle de Données sur Bases de Données Chiffrées : Mélange de Chiffrement Fonctionnel et Confidentialité Différentielle Calculatoire
No full textIn our current digitalized society, data is ruling the world. But as it is most of the time related to individuals, its exploitation should respect the privacy of the latter. This issue has raised the differential privacy paradigm, which permits to protect individuals when querying databases containing data about them. But with the emergence of cloud computing, it is becoming increasingly necessary to also consider the confidentiality of "on-cloud'' storage confidentiality of such vast databases, using encryption techniques. This thesis studies how to provide both privacy and confidentiality of such outsourced databases by mixing two primitives: computational differential privacy and functional encryption. First, we study the relationship between computational differential privacy and functional encryption for randomized functions in a generic way. We analyze the privacy of the setting where a malicious analyst may access the encrypted data stored in a server, either by corrupting or breaching it, and prove that a secure randomized functional encryption scheme supporting the appropriate family of functions guarantees the computational differential privacy of the system. Second, we construct efficient randomized functional encryption schemes for certain useful families of functions, and we prove them secure in the standard model under well-known assumptions. The families of functions considered are linear functions, used for example in counting queries, histograms and linear regressions, and quadratic functions, used for example in quadratic regressions and hypothesis testing. The schemes built are then used together with the first result to construct encrypted databases for their corresponding family of queries. Finally, we implement both randomized functional encryption schemes to analyze their efficiency. This shows that our constructions are practical for databases with up to 1 000 000 entries in the case of linear queries and databases with up to 10 000 database entries in the case of quadratic queries.Dans l'actuelle société numérique, les données dominent le monde. Associées la plupart du temps à des individus, leur exploitation doit respecter la vie privée de ces derniers. Cette contrainte a donné naissance au paradigme de confidentialité différentielle, qui permet de protéger les individus lors de requêtes sur des bases contenant des données les concernant. Mais avec l'émergence du "cloud computing'', il devient nécessaire de prendre en compte la confidentialité du stockage de ces dernières dans le cloud, en utilisant du chiffrement. Cette thèse étudie comment assurer à la fois la confidentialité et le respect de la vie privée de ces bases de données externalisées en combinant deux primitives : la confidentialité différentielle calculatoire et le chiffrement fonctionnel. Dans un premier temps, nous étudions les liens entre la confidentialité différentielle calculatoire et le chiffrement fonctionnel pour des fonctions aléatoires d'un point de vue générique. Nous analysons la confidentialité dans un cadre où un analyste malicieux peut accéder aux données chiffrées stockés dans un serveur soit par corruption soit par brèche de sécurité, et nous prouvons qu'un schéma de chiffrement fonctionnel aléatoire sûr et pour la famille de fonctions appropriée garantie la confidentialité différentielle calculatoire du système. Dans second temps, nous construisons des schémas de chiffrement fonctionnel aléatoire pour certaines familles de fonctions utiles, et nous les prouvons sûrs dans le modèle standard sous des hypothèses très étudiées. Les familles de fonctions que nous étudions sont les fonctions linéaires, utilisées par exemple pour requêtes de comptage, des histogrammes et régressions linéaires, et les fonctions quadratiques, utilisées par exemple pour régressions quadratiques et tests d'hypothèses. Les schémas proposés sont utilisés avec le premier résultat pour construire des bases des données chiffrées pour fonctions linéaires et quadratiques respectivement. Finalement, nous implémentons les deux schémas de chiffrement fonctionnel pour analyser leur efficacité. Cela montre que nos constructions sont pratiques pour des bases de données avec 1 000 000 entrées pour des requêtes linéaires et des bases de données avec 10 000 entrées pour des requêtes quadratiques
RLWE-based distributed key generation and threshold decryption
Get PDFEver since the appearance of quantum computers, prime factoring and discrete logarithm based cryptography has been put in question, giving birth to the so called post-quantum cryptography. The most prominent field in post-quantum cryptography is lattice-based cryptography, protocols that are proved to be as difficult to break as certain difficult lattice problems like Learning With Errors (LWE) or Ring Learning With Errors (R-LWE). This Master s Degree Thesis forwards and elevates the work done in the Bachelor s Degree Thesis "Lattice-based Threshold Cryptography" by taking the R-LWE-based protocols specified there and giving more accurate and improved proofs of correctness and security, developing an original proposal for dispute resolution throughout both protocols, making an analysis of the specific hardness of breaking security of the protocol and analyzing a given implementation of both protocols in C
Simulation Secure Multi-input Quadratic Functional Encryption
No full textInternational audienceMulti-input functional encryption is a primitive that allows for the evaluation of an -ary function over multiple ciphertexts, without learning any information about the underlying plaintexts. This type of computation is useful in many cases where one has to compute over encrypted data, such as privacy-preserving cloud services, federated learning, or more generally delegation of computation from multiple clients. In this work we propose the first secret-key multi-input quadratic functional encryption scheme satisfying simulation security. On contrary, current constructions supporting quadratic functionalities, proposed by Agrawal et al. in CRYPTO '21 and TCC '22, only reach indistinguishibility-based security. Our proposed construction is generic, and for a concrete instantiation, we propose a new function-hiding innerproduct functional encryption scheme proven simulation secure against one challenge ciphertext in the standard model, which is of independent interest
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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