Naor-Yung paradigm with shared randomness and applications

The Naor-Yung paradigm (Naor and Yung, STOC’90) allows to generically boost security under chosen-plaintext attacks (CPA) to security against chosen-ciphertext attacks (CCA) for public-key encryption (PKE) schemes. The main idea is to encrypt the plaintext twice (under independent public keys), and to append a non-interactive zero-knowledge (NIZK) proof that the two ciphertexts indeed encrypt the same message. Later work by Camenisch, Chandran, and Shoup (Eurocrypt’09) and Naor and Segev (Crypto’09 and SIAM J. Comput.’12) established that the very same techniques can also be used in the settings of key-dependent message (KDM) and key-leakage attacks (respectively). In this paper we study the conditions under which the two ciphertexts in the Naor-Yung construction can share the same random coins. We find that this is possible, provided that the underlying PKE scheme meets an additional simple property. The motivation for re-using the same random coins is that this allows to design much more efficient NIZK proofs. We showcase such an improvement in the random oracle model, under standard complexity assumptions including Decisional Diffie-Hellman, Quadratic Residuosity, and Subset Sum. The length of the resulting ciphertexts is reduced by 50%, yielding truly efficient PKE schemes achieving CCA security under KDM and key-leakage attacks. As an additional contribution, we design the first PKE scheme whose CPA security under KDM attacks can be directly reduced to (low-density instances of) the Subset Sum assumption. The scheme supports keydependent messages computed via any affine function of the secret ke

Déterminants socioculturels de l’apprentissage du discours décontextualisé en milieu scolaire : vers un cadre théorique intégré

La disparité entre la performance scolaire des enfants des groupes majoritaire et minoritaire devrait normalement diminuer avec les années de scolarisation. C’est pourtant l’inverse qui se produit et ce paradoxe, bien connu des chercheurs dans le domaine, n’a pas encore reçu d’explication satisfaisante.Cet article se propose de tracer les grandes lignes d’un cadre théorique qui, tout en aidant à saisir la grande complexité du problème, permet d’approfondir la compréhension d’un de ses aspects : l’interaction entre la culture et la cognition.La théorie des schémas est utilisée pour expliquer certaines difficultés rencontrées dans la pratique de la lecture et de l’écriture, en se basant sur le fait que des expériences culturelles disparates donnent lieu au développement de schémas distincts chez les individus de cultures différentes.Le processus de scolarisation, qui devrait consister à étendre le répertoire de schémas cognitifs, sociaux et linguistiques de l’enfant est à l’origine d’un aspect du paradoxe étudié; en étant axés sur les habiletés de base, les programmes scolaires offrent un contexte peu propice au développement de certains schémas cognitifs essentiels.The disparity between the scholastic performance of children belonging to majority and minority groups should normally decrease with schooling. Nevertheless, it is the opposite that is observed and this paradox, well-known to the researchers in this field, has not yet received a satisfactory explanation.This paper proposes to sketch the main lines of a theoretical framework that helps to understand the great complexity of the problem and allows a deeper comprehension of one of its aspects: the interaction between culture and cognition.Schema theory is used to explain certain difficulties in reading and writing, based on the fact that differences in cultural experiences give rise to the development of different schemas for individuals coming from different cultures.The schooling process, which should contribute to extending the repertory of the child's cognitive, social and linguistic schemas, is in fact at the origin of one aspect of the paradox in question; being centrated on basic skills, scholastic programs offer a context that is not conductive to the emergence of certain essential cognitive schemas

SYSTEM AND METHOD FOR REVOKING COMPROMISED CRYPTOGRAPHIC KEY FROM DATABASE

The present disclosure provides a system and a method for revoking compromised cryptographic key from a database. The proposed system provides a database which is a graph that stores information on dependencies between a working key and cryptographic algorithms and keys used in establishing the working keys. The proposed system upon identifying the compromised keys revokes the compromised cryptographic keys and corresponding keys from the database. The proposed system provides data security and an efficient revocation process of the compromised cryptographic keys

Introduction to Multiple Literacies Theory: A Deleuzian Perspective

This book comes at a time when literacy has perhaps been overly researched and theorized around the world. Governments are especially interested in investigating and collecting data about how their citizens become literate. One might legitimately ask the question: Why do we need more research and theory about literacy? The short answer to this question is that we do not need more information about the processes of literacy. What we do need is work that combines data with a theoretical frame that makes sense of the diverse literacy practices and complex demographics of populations through which literacy is now apparent. In poststructural terms, it could be said that literacy research is an area of `overcoding (Webb, 2009). This means that the balance between signification and the content of the signification is out of phase. For example, the enormous attention that has been given to reading comprehension in educational research is incongruous with the role that reading comprehension plays in the educational process. Reading comprehension has been over-coded by outside bodies solely interested in the results of reading comprehension, i.e., literacy tests. This volume addresses this situation by going outside of the norm, and proposing a new way of conceptualizing literacy, Multiple Literacies Theory (Masny, 2006), combined with data to solidify this view

Экологическая парадигма

Предлагается один из возможных вариантов решения проблемы экологической парадигмы. С точки зрения автора, экологическая парадигма является специфической формой социальной парадигмы. Она формируется на определенных этапах становления экологического сознания. Процессы глобализации, происходящие в мире, предполагают нравственное наполнение человеческой деятельности особенно в части ее отношения к природе. Философское понимание системы «Природа - Общество» связано с восприятием дихотомичности социального мышления, являющейся основой существования нескольких разновидностей экологической парадигмы. Сложность и противоречивость восприятия экологических проблем, их решение приобретает в современном мире планетарный характер

Authentication from Weak PRFs with Hidden Auxiliary Input

In this work, we study a class of randomized weak pseudorandom functions, which we call weak PRFs with hidden auxiliary input (HIwPRF). Compared to Learning Parity with Noise (LPN) or Learning with Errors (LWE) based randomized weak PRFs, it provides less algebraic structure such that many known techniques and constructions do not translate to this class. We investigate the potential of HIwPRFs for secure message and user authentication. We construct a protocol that gives as strong security guarantees when instantiated with a HIwPRF as known from weak PRF, LPN or LWE based protocols

On Parfit’s Wide Dual Person-Affecting Principle

In the posthumously published ‘Future People, the Non-Identity Problem, and Person-Affecting Principles’, Derek Parfit presents a novel axiological principle which he calls the Wide Dual Person-Affecting Principle and claims that it does not imply the Repugnant Conclusion. This paper shows that even the best version of Parfit's principle cannot avoid this conclusion. That said, accepting such a principle makes embracing the Repugnant Conclusion more justifiable. This paper further addresses important questions which Parfit left unanswered concerning: the relative importance of individual and collective goodness, comparisons involving unequal outcomes, how to understand individual goodness, and whether incomparability at the level of individual goodness implies incomparability at the level of overall goodness

Representations of the Vietnam War in the comic book "The Other Side"

The purpose of this article is to present the portrait of the Vietnam War (1965-1975) in the comic book The Other Side by Jason Aaron and Cameron Stewart, from the point of view of the historian researching this conflict. I analyze this comic in two dimensions: juxtaposing its narrative with historical reality and with other narratives about the Vietnam War present in American culture. I examine if The Other Side repeats some of the “Vietnam war myths” as well, especially because of the claims of its authors. I take a closer look to discern what interpretation of the history of the Vietnam War was made in the comic. I also present how the authors used events, characters and historical terms to give their work an anti-war overtone. The influence of fiction, memoirs and works of writers such as Ambrose Bierce, Gustav Hasford as well as the reporter group called Snuffies on the final shape of the comic is also discussed