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Browsing Congressos (Departament de Tecnologies de la Informació i les Comunicacions) by Author "Ràfols, Carla"

Browsing Congressos (Departament de Tecnologies de la Informació i les Comunicacions) by Author "Ràfols, Carla"

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  • An algebraic framework for Diffie-Hellman assumptions
    Escala, Alex; Herold, Gottfried; Kiltz, Eike; Ràfols, Carla; Villar, Jorge L. (Springer, 2013)
    We put forward a new algebraic framework to generalize and analyze Di_e-Hellman like Decisional Assumptions which allows us to argue about security and applications by considering only algebraic properties. Our D`;k-MDDH ...
  • Breaking Yum and Lee generic constructions of certificate-less and certificate-based encryption schemes
    Galindo, David; Morillo, Paz; Ràfols, Carla (Springer, 2006)
    Identity-based public key cryptography is aimed at simplifying the management of certificates in traditional public key infrastructures by means of using the identity of a user as its public key. The user must identify ...
  • CCA2-secure threshold broadcast encryption with shorter ciphertexts
    Daza, Vanesa; Herranz, Javier; Morillo, Paz; Ràfols, Carla (Springer, 2007)
    In a threshold broadcast encryption scheme, a sender chooses (ad-hoc) a set of n receivers and a threshold t, and then encrypts a message by using the public keys of all the receivers, in such a way that the original ...
  • Constant size ciphertexts in threshold attribute-based encryption
    Herranz, Javier; Laguillaumie, Fabien; Ràfols, Carla (Springer, 2010)
    Attribute-based cryptography has emerged in the last years as a promising primitive for digital security. For instance, it provides good solutions to the problem of anonymous access control. In a ciphertext- policy ...
  • Identity-based lossy trapdoor functions: new definitions, hierarchical extensions, and implications
    Escala, Alex; Herranz, Javier; Libert, Benoît; Ràfols, Carla (Springer, 2014)
    Lossy trapdoor functions, introduced by Peikert and Waters (STOC’08), have received a lot of attention in the last years, because of their wide range of applications. The notion has been recently extended to the identity-based ...
  • The Kernel Matrix Diffie-Hellman assumption
    Morillo, Paz; Ràfols, Carla; Villar, Jorge L. (Springer, 2016)
    We put forward a new family of computational assumptions, the Kernel Matrix Diffi-Hellman Assumption. Given some matrix A sampled from some distribution D, the kernel assumption says that it is hard to find \in the exponent" ...
  • New techniques for non-interactive shuffle and range arguments
    González, Alfonso; Ràfols, Carla (Springer, 2016)
    We construct the most efficient non-interactive Argument of Correctness of a Shuffle and Range Argument under falsifiable assumptions in asymmetric bilinear groups. Our constructions use as a common building block a novel ...
  • New techniques for structural batch verification in bilinear groups with applications to groth-Sahai proofs
    Herold, Gottfried; Hoffmann, Max; Klooß, Michael; Ràfols, Carla; Rupp, Andy (ACM Association for Computer Machinery, 2017)
    Bilinear groups form the algebraic setting for a multitude of important cryptographic protocols including anonymous credentials, e-cash, e-voting, e-coupon, and loyalty systems. It is typical of such crypto protocols that ...
  • Polynomial spaces: a new framework for composite to-prime-order transformations
    Herold, Gottfried; Hesse, Julia; Hofheinz, Dennis; Ràfols, Carla; Rupp, Andy (Springer, 2014)
    At Eurocrypt 2010, Freeman presented a framework to convert cryptosystems based on composite-order groups into ones that use prime-order groups. Such a transformation is interesting not only from a conceptual point of view, ...
  • QA-NIZK arguments in asymmetric groups: new tools and new constructions
    González, Alonso; Hevia, Alejandro; Ràfols, Carla (Springer, 2015)
    A sequence of recent works have constructed constant-size quasi-adaptive (QA) NIZK arguments of membership in linear subspaces of ^Gm, where ^G is a group equipped with a bilinear map e : G x H --> T. Although applicable ...
  • QA-NIZK arguments of same opening for bilateral commitments
    Ràfols, Carla; Silva, Javier (Springer, 2020)
    Zero-knowledge proofs of satisfiability of linear equations over a group are often used as a building block of more complex protocols. In particular, in an asymmetric bilinear group we often have two commitments in different ...
  • Short attribute-based signatures for threshold predicates
    Herranz, Javier; Laguillaumie, Fabien; Libert, Benoît; Ràfols, Carla (Springer, 2012)
    Attribute-based cryptography is a natural solution for fine- grained access control with respect to security policies. In the case of attribute-based signatures (ABS), users obtain from an authority their secret keys as a ...
  • Shorter quadratic QA-NIZK proofs
    Daza, Vanesa; González, Alonso; Pindado, Zaira; Ràfols, Carla; Silva, Javier (Springer, 2019)
    Despite recent advances in the area of pairing-friendly Non-Interactive Zero-Knowledge proofs, there have not been many efficiency improvements in constructing arguments of satisfiability of quadratic (and larger degree) ...
  • Signatures of knowledge for boolean circuits under standard assumptions
    Baghery, Karim; González, Alonso; Pindado, Zaira; Ràfols, Carla (Springer, 2020)
    This paper constructs unbounded simulation sound proofs for boolean circuit satisfiability under standard assumptions with proof size O(n+d) bilinear group elements, where d is the depth and n is the input size of the ...
  • Stretching Groth-Sahai: NIZK proofs of partial satisfiability
    Ràfols, Carla (Springer, 2015)
    Groth, Ostrovsky and Sahai constructed a non-interactive Zap for NP-languages by observing that the common reference string of their proof system for circuit satisfiability admits what they call correlated key generation. ...
  • The Security of all bits using list decoding
    Morillo, Paz; Ràfols, Carla (Springer, 2009)
    The relation between list decoding and hard-core predicates has provided a clean and easy methodology to prove the hardness of certain predicates. So far this methodology has only been used to prove that the O(log logN) ...
  • Updateable inner product argument with logarithmic verifier and applications
    Daza, Vanesa; Ràfols, Carla; Zacharakis, Alexandros (Springer, 2020)
    We propose an improvement for the inner product argument of Bootle et al. (EUROCRYPT’16). The new argument replaces the unstructured common reference string (the commitment key) by a structured one. We give two instantiations ...

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