Now showing items 1-12 of 46

    • Improving the linear programming technique in the search for lower bounds in secret sharing 

      Farràs Ventura, Oriol; Kaced, Tarik; Martín Mollevi, Sebastià; Padró Laimon, Carles (2020-11)
      Article
      Restricted access - publisher's policy
      We present a new improvement in the linear programming technique to derive lower bounds on the information ratio of secret sharing schemes. We obtain non-Shannon-type bounds without using information inequalities explicitly. ...
    • Attacking pairing-free attribute-based encryption schemes 

      Herranz Sotoca, Javier (Institute of Electrical and Electronics Engineers (IEEE), 2020)
      Article
      Open Access
      Combining several results that have been published in the last years, it is known that it is impossible to design simple and secure attribute-based encryption schemes that work in (classical) settings like the RSA or the ...
    • Mixed integration of CDIO skills into telecommunication engineering curricula 

      Sayrol Clols, Elisa; Bragós Bardia, Ramon; Alarcón Cot, Eduardo José; Cabrera-Bean, Margarita; Calveras Augé, Anna M.; Comellas Colomé, Jaume; O'Callaghan Castellà, Juan Manuel; Pegueroles Vallés, Josep R.; Pla, Enrique; Prat Viñas, Lluís; Sáez Moreno, Germán; Sardà Ferrer, Joan; Tallon Montoro, Carme (2010)
      Article
      Open Access
      Spain has been intensively involved in designing engineering curricula for the last two years and next academic year all engineering schools will be deploying all bachelor programs adapted to the EHEA and to the Spanish ...
    • Secret sharing schemes for (k, n)-consecutive access structures 

      Herranz Sotoca, Javier; Sáez Moreno, Germán (Springer, 2018-09-01)
      Article
      Restricted access - publisher's policy
      We consider access structures over a set P of n participants, defined by a parameter k with 1 = k = n in the following way: a subset is authorized if it contains participants i, i + 1,...,i + k - 1, for some i ¿ {1,...,n-k+1}. ...
    • On the information ratio of non-perfect secret sharing schemes 

      Farràs Ventura, Oriol; Hansen, Torben; Kaced, Tarik; Padró Laimon, Carles (2017-12-01)
      Article
      Open Access
      A secret sharing scheme is non-perfect if some subsets of players that cannot recover the secret value have partial information about it. The information ratio of a secret sharing scheme is the ratio between the maximum ...
    • An algebraic framework for Diffie-Hellman assumptions 

      Escala Ribas, Alex; Herold, Gottfried; Kiltz, Eike; Ràfols Salvador, Carla; Villar Santos, Jorge Luis (2017-01)
      Article
      Open Access
      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 ...
    • Equivalences and black-box separations of Matrix Diffie-Hellman problems 

      Villar Santos, Jorge Luis (2017-02)
      Article
      Open Access
      In this paper we provide new algebraic tools to study the relationship between different Matrix Diffie-Hellman (MDDH) Problems, which are recently introduced as a natural generalization of the so-called Linear Problem. ...
    • Attribute-based encryption implies identity-based encryption 

      Herranz Sotoca, Javier (2017-11-01)
      Article
      Open Access
      In this study, the author formally proves that designing attribute-based encryption schemes cannot be easier than designing identity-based encryption schemes. In more detail, they show how an attribute-based encryption ...
    • On the optimization of bipartite secret sharing schemes 

      Farràs Ventura, Oriol; Metcalf-Burton, Jessica Ruth; Padró Laimon, Carles; Vázquez González, Leonor (2012-05-01)
      Article
      Open Access
      Optimizing the ratio between the maximum length of the shares and the length of the secret value in secret sharing schemes for general access structures is an extremely difficult and long-standing open problem. In this ...
    • Ideal hierarchical secret sharing schemes 

      Farràs Ventura, Oriol; Padró Laimon, Carles (2012-01-24)
      Article
      Open Access
      Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention since the invention of secret sharing until nowadays. Several constructions of ideal ...
    • Finding lower bounds on the complexity of secret sharing schemes by linear programming 

      Padró Laimon, Carles; Vázquez González, Leonor; Yang, An (2013-05-01)
      Article
      Open Access
      Optimizing the maximum, or average, length of the shares in relation to the length of the secret for every given access structure is a difficult and long-standing open problem in cryptology. Most of the known lower bounds ...
    • Signcryption schemes with threshold unsigncryption, and applications 

      Herranz Sotoca, Javier; Ruiz, Alexandre; Sáez Moreno, Germán (2014-03)
      Article
      Open Access
      The goal of a signcryption scheme is to achieve the same functionalities as encryption and signature together, but in a more efficient way than encrypting and signing separately. To increase security and reliability in ...