Now showing items 21-34 of 34

    • GEOMETRIA DIFERENCIAL | FINAL 

      Amorós Torren, Jaume; Gálvez Carrillo, Imma; Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2021-05-03)
      Exam
      Restricted access to the UPC academic community
    • Ideal hierarchical secret sharing schemes 

      Farràs Ventura, Oriol; Padró Laimon, Carles (Springer, 2010)
      Conference report
      Open Access
      Hierarchical secret sharing is among the most natural generalizations of threshold secret sharing, and it has attracted a lot of attention from the invention of secret sharing until nowadays. Several constructions of ideal ...
    • 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 ...
    • 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
      Open Access
      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. ...
    • Linear threshold multisecret sharing schemes 

      Farras Ventura, Oriol; Gràcia Rivas, Ignacio; Martín Mollevi, Sebastià; Padró Laimon, Carles (Springer Verlag, 2009)
      Conference report
      Open Access
      In a multisecret sharing scheme, several secret values are distributed among a set of n users, and each secret may have a differ- ent associated access structure. We consider here unconditionally secure schemes with ...
    • Natural generalizations of threshold secret sharing 

      Farràs Ventura, Oriol; Padró Laimon, Carles; Xing, Chaoping; Yang, An (2014-01-14)
      Article
      Open Access
      We present new families of access structures that, similarly to the multilevel and compartmented access structures introduced in previous works, are natural generalizations of threshold secret sharing. Namely, they admit ...
    • On secret sharing schemes, matroids and polymatroids 

      Martí Farré, Jaume; Padró Laimon, Carles (2010-10)
      Article
      Restricted access - publisher's policy
      The complexity of a secret sharing scheme is defined as the ratio between the maximum length of the shares and the length of the secret. The optimization of this parameter for general access structures is an important and ...
    • On secret sharing with nonlinear product reconstruction 

      Cascudo, Ignacio; Cramer, Ronald; Mirandola, Diego; Padró Laimon, Carles; Xing, Chaoping (2015-06-24)
      Article
      Open Access
      Multiplicative linear secret sharing is a fundamental notion in the area of secure multi- party computation (MPC) and, since recently, in the area of two-party cryptography as well. In a nutshell, this notion guarantees ...
    • 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 ...
    • On the optimization of bipartite secret sharing schemes 

      Farras Ventura, Oriol; Metcalf-Burton, Jessica Ruth; Padró Laimon, Carles; Vázquez González, Leonor (2010)
      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 ...
    • 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 ...
    • On the representability of the biuniform matroid 

      Ball, Simeon Michael; Padró Laimon, Carles; Weiner, Zsuzsa; Xing, Chaoping (2013-08-22)
      Article
      Open Access
      Every biuniform matroid is representable over all sufficiently large fields. But it is not known exactly over which finite fields they are representable, and the existence of efficient methods to find a representation for ...
    • Optimal non-perfect uniform secret sharing schemes 

      Farràs Ventura, Oriol; Hansen, Torben; Kaced, Tarik; Padró Laimon, Carles (Springer, 2014)
      Conference report
      Open Access
      A secret sharing scheme is non-perfect if some subsets of participants 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 ...
    • Secret sharing, rank inequalities, and information inequalities 

      Martín Mollevi, Sebastià; Padró Laimon, Carles; Yang, An (2016-01)
      Article
      Open Access
      Beimel and Orlov proved that all information inequalities on four or five variables, together with all information inequalities on more than five variables that are known to date, provide lower bounds on the size of the ...