L'objectiu del grup de recerca és l'estudi dels problemes matemàtics de més actualitat en el camp de la criptologia. Els temes de recerca se centren principalment en els aspectes següents:
- Criptografia distribuïda. Les parts implicades en el protocol criptogràfic són col·lectius que hauran de compartir certa informació secreta.
En aquest punt cal destacar la computació multipart i els esquemes de distribució de secrets.
- Protocols criptogràfics segurs. En aquest punt es tracta d'analitzar i dissenyar protocols, tant de xifratge com de signatura digital, que siguin eficients i segurs. La definició de seguretat també és tema d'estudi.
Destaquem també l'estudi de les aplicacions de les corbes el·líptiques a la criptografia.

The main goal of the research group is the study of mathematical problems in cryptology.
The main research areas are the following:
- Distributed cryptography. The groups working on cryptographic protocols have to share secret information. Multi-party computation and secret-sharing schemes are also studied.
- Secure cryptographic protocols. The aim is to analyse and design efficient and secure protocols, both for encryption and for digital signatures.
The definition of security is also the subject of research. The applications of elliptic curves in cryptography are also studied.

The main goal of the research group is the study of mathematical problems in cryptology.
The main research areas are the following:
- Distributed cryptography. The groups working on cryptographic protocols have to share secret information. Multi-party computation and secret-sharing schemes are also studied.
- Secure cryptographic protocols. The aim is to analyse and design efficient and secure protocols, both for encryption and for digital signatures.
The definition of security is also the subject of research. The applications of elliptic curves in cryptography are also studied.

Recent Submissions

  • 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. ...
  • Equivalences and Black-Box Separations of Matrix Diffie-Hellman Problems 

    Villar Santos, Jorge Luis (Springer, 2017)
    Conference lecture
    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 ...
  • 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 ...
  • 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 ...
  • 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 ...

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