Now showing items 1-20 of 20

  • Alan Turing: màquines i enigmes 

    Padró Laimon, Carles (2015-09-30)
    Audiovisual
    Open Access
    La lliçó inaugural, impartida per Carles Padró, professor titular de la UPC al Departament de Matemàtica Aplicada IV, portarà per títol: Alan Turing, màquines i enigmes. En el decurs de la conferència s'explicarà les dues ...
  • CÀLCUL EN UNA VARIABLE 

    Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2016-01-14)
    Exam
    Restricted access to the UPC academic community
  • CÀLCUL EN UNA VARIABLE 

    Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2018-01-08)
    Exam
    Restricted access to the UPC academic community
  • CÀLCUL EN UNA VARIABLE 

    Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2017-07-06)
    Exam
    Restricted access to the UPC academic community
  • CÀLCUL EN UNA VARIABLE 

    Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2017-01-12)
    Exam
    Restricted access to the UPC academic community
  • CÀLCUL EN UNA VARIABLE 

    Padró Laimon, Carles (Universitat Politècnica de Catalunya, 2016-06-30)
    Exam
    Restricted access to the UPC academic community
  • Extending Brickell-Davenport theorem to non-perfect secret sharing schemes 

    Farràs Ventura, Oriol; Padró Laimon, Carles (2015-02)
    Article
    Open Access
    One important result in secret sharing is the Brickell-Davenport Theorem: every ideal perfect secret sharing scheme de nes a matroid that is uniquely determined by the access structure. Even though a few attempts have been ...
  • 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 ...
  • 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 ...
  • 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 ...
  • 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 ...