Browsing by Author "Ràfols, Carla"

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  • 'Ad-hoc' threshold broadcast encryption with shorter ciphertexts
    Daza, Vanesa; Herranz, Javier; Morillo, Paz; Ràfols, Carla (Elsevier, 2008)
    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 ...
  • Algebraic techniques for universal succinct arguments
    Zapico Barrionuevo, Victoria Arantxa (Universitat Pompeu Fabra, 2022-11-02)
    In this thesis, we make theoretical and practical contributions to the design of succinct arguments with universal setups in the pairing-based setting. We first introduce a new primitive, Checkable Subspace Sampling (CSS) ...
  • 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 ...
  • Attribute-based encryption schemes with constant-size ciphertexts
    Attrapadung, Nuttapong; Herranz, Javier; Laguillaumie, Fabien; Libert, Benoît; De Panafieu, Elie; Ràfols, Carla (Elsevier, 2012)
    Attribute-based encryption (ABE), as introduced by Sahai and Waters, allows for fine- grained access control on encrypted data. In its key-policy flavor (the dual ciphertext-policy scenario proceeds the other way around), ...
  • 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 ...
  • Dynamic group size accreditation and group discounts preserving anonymity
    Domingo-Ferrer, Josep; Blanco-Justicia, Alberto; Ràfols, Carla (Springer, 2018)
    Group discounts are used by vendors and authorities to encourage certain behaviors. For example, group discounts can be applied to highway tolls to encourage ride sharing, or by museum managers to ensure a minimum number ...
  • 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 ...
  • On dynamic distribution of private keys over MANETs
    Daza, Vanesa; Morillo, Paz; Ràfols, Carla (Elsevier, 2007)
    Identity-Based cryptography has been proposed in mobile ad-hoc networks (MANETs) to provide security. However, the figure of the Private Key Generator (PKG) is not adequate in the MANET setting, since it may not be reachable ...
  • Pairing-based non-interactive zero-knowledge arguments and applications
    Pindado, Zaira (Universitat Pompeu Fabra, 2021-04-01)
    Elliptic curves with a bilinear map, or pairing, have a rich algebraic structure that has been fundamental to develop practical Non-Interactive Zero-Knowledge (NIZK) proofs. On the theoretical side, we explore how efficient ...
  • 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 ...
  • Relations between semantic security and anonymity in identity-based encryption
    Herranz, Javier; Laguillaumie, Fabien; Ràfols, Carla (Elsevier, 2011)
    Semantic security and anonymity are the two main properties that an identity-based encryption scheme can satisfy. Such properties can be de ned in either an adaptive or a selective scenario, which di er on the moment where ...
  • 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) ...

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