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  • Identity-based lossy trapdoor functions: new definitions, hierarchical extensions, and implications

     Escala Ribas, Alex; Herranz Sotoca, Javier; Libert, Benoit; Rafols Salvador, Carla
    Lecture notes in computer science
    Vol. 8383, p. 239-256
    DOI: 10.1007/978-3-642-54631-0_14
    Date of publication: 2014-03
    Journal article

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  • Hacia una sociedad digital segura: avances matemáticos en criptografía y su impacto en las tecnologías digitales

     Morillo Bosch, Maria Paz; Saez Moreno, German; Martin Mollevi, Sebastia; González Vasco, Maria Isabel; Steinwandt, Rainer; d'Arco, Paolo; Kiltz, Eike; Padro Laimon, Carles; Herranz Sotoca, Javier; Pérez del Pozo, Ángel; Villar Santos, Jorge Luis
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  • Identity-based lossy trapdoor functions: new definitions, hierarchical extensions, and implications

     Escala Ribas, Alex; Herranz Sotoca, Javier; Libert, Benoit; Rafols Salvador, Carla
    International Conference on Practice and Theory in Public Key Cryptography
    p. 239-256
    DOI: 10.1007/978-3-642-54631-0-14
    Presentation's date: 2014-03
    Presentation of work at congresses

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    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 setting by Bellare et al. (Eurocrypt'12). An identity-based trapdoor function (IB-TDF) satisfying the lossy property introduced by Bellare et al. can be used to construct other cryptographic primitives in the identity-based setting: encryption schemes with semantic security under chosen-plaintext attacks, deterministic encryption schemes, and hedged encryption schemes that maintain some security when messages are encrypted using randomness of poor quality. However, the constructed primitives can be proved secure only against selective adversaries who select the target identity upfront. Our first contribution is an alternative definition for the lossiness of an identity-based trapdoor function. We prove that an IB-TDF satisfying the new property can be used to construct all the aforementioned primitives, in the identity-based setting, with security against adaptive adversaries. We further consider the new definition and its implications in the more general scenario of hierarchical identity-based cryptography, which has proved very useful both for practical applications and to establish theoretical relations with other cryptographic primitives (including encryption with chosen-ciphertext security or with forward-security). As a second contribution, we describe a pairing-based hierarchical IB-TDF satisfying the new definition of lossiness against either selective or, for hierarchies of constant depth, adaptive adversaries. This is also the first example of hierarchical trapdoor functions based on traditional (i.e., non-lattice-related) number theoretic assumptions. As a direct consequence of our two contributions, we obtain a hierarchical identity-based (HIB) encryption scheme with chosen-plaintext security, a HIB deterministic encryption scheme and a HIB hedged encryption scheme, all of them with security against adaptive adversaries.

  • Sharing many secrets with computational provable security

     Herranz Sotoca, Javier; Ruiz, Alexandre; Saez Moreno, German
    Information processing letters
    Vol. 113, num. 14-16, p. 572-579
    DOI: 10.1016/j.ipl.2013.05.003
    Date of publication: 2013-07
    Journal article

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    We propose in this work two new multi-secret sharing schemes, that allow to distribute l different secrets among a set P={P1,¿,Pn}P={P1,¿,Pn} of players, each one according to a (possibly different) access structure. The two schemes are proved to enjoy computational security, by reduction to the semantic security of the underlying symmetric encryption scheme. The two security proofs are in the standard model and provide the exact relation between the security of the involved primitives. As far as we know, this is the first formal security analysis for a computational multi-secret sharing scheme in the literature. We compare the two new schemes, taking into account their efficiency properties, their security analysis and possible extensions. One of the schemes has very short secret shares (independently of the number l of secrets) and can be easily extended to work without any trusted dealer. The other scheme has longer secret shares and the extension to work without a trusted dealer is much more complicated, but on the other hand it produces shorter public outputs and the security relation with the underlying symmetric encryption scheme is better, which may have consequences in the final efficiency of the scheme.

  • Contributions to Secret Sharing and Other Distributed Cryptosystems  Open access

     Ruiz Rodriguez, Alexandre
    Universitat Politècnica de Catalunya
    Theses

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    Avui en dia les persones estan implicades cada dia més en diferents activitats digitals tant en la seva vida professional com en el seu temps lliure. Molts articles de paper, com diners i tiquets, estan sent reemplaçats més i més per objectes digitals. La criptografia juga un paper crucial en aquesta transformació, perquè proporciona seguretat en la comunicació entre els diferents participants que utilitzen un canal digital. Depenent de la situació específica, alguns requisits de seguretat en la comunicació poden incloure privacitat (o confidencialitat), autenticitat, integritat o no-repudi. En algunes situacions, repartir l'operació secreta entre un grup de participants fa el procés més segur i fiable que quan la informació secreta està centralitzada en un únic participant; la criptografia distribuïda és l¿àrea de la criptografia que estudia aquestes situacions. Aquesta tesi tracta de primitives relacionades amb el camp de la criptografia distribuïda. Primer, estudiem esquemes ¿signcryption¿, que ofereixen a la vegada les funcionalitats de xifrat i signatura, on l'operació de ¿unsigncryption¿ està distribuïda. Considerem aquesta primitiva des d¿un punt de vista teòric i establim un marc de seguretat per ella. Llavors, presentem dos esquemes ¿signcryption¿ amb operació de ¿unsigncryption¿ determinada per una estructura llindar, cada un amb diferents propietats. A més, utilitzem la seva propietat d¿autenticitat per desenvolupar una nova primitiva: signatures digitals amb verificació distribuïda. El segon bloc de la tesi tracta la primitiva dels esquemes de compartició de multi-secrets. Després de demostrar algunes limitacions en l¿eficiència dels esquemes de compartició de multi-secrets en un escenari de teoria de la informació, presentem diversos esquemes de compartició de multi-secrets amb seguretat computacional demostrable. Finalment, utilitzem els resultats obtinguts en els esquemes de compartició de multi-secrets per generalitzar el paradigma tradicional de la criptografia distribuïda (amb una única política de subconjunts autoritzats) a un marc multi-política, i presentem un esquema de desxifrat distribuït amb multi-política i un esquema de signatura distribuïda amb multi-política. A més, donem indicacions de com es poden aplicar els nostres esquemes de compartició de multi-secrets en el disseny d¿altres criptosistemes amb multi-política, com per exemple els esquemes ¿signcryption¿ considerats en aquesta tesi.Per tots els esquemes proposats al llarg d¿aquesta tesi, seguim la mateixa estructura formal. Després de definir els protocols de la primitiva primitius i el model de seguretat corresponent, proposem el nou esquema i demostrem formalment la seva seguretat, mitjançant una reducció a algun problema matemàtic computacionalment difícil.

    The present thesis deals with primitives related to the eld of distributed cryptography. First, we study signcryption schemes, which provide at the same time the functionalities of encryption and signature, where the unsigncryption operation is distributed. We consider this primitive from a theoretical point of view and set a security framework for it. Then, we present two signcryption schemes with threshold unsigncryption, with di erent properties. Furthermore, we use their authenticity property to apply them in the development of a di erent primitive: digital signatures with distributed veri cation. The second block of the thesis deals with the primitive of multi-secret sharing schemes. After stating some e ciency limitations of multi-secret sharing schemes in an information-theoretic scenario, we present several multi-secret sharing schemes with provable computational security. Finally, we use the results in multi-secret sharing schemes to generalize the traditional framework of distributed cryptography (with a single policy of authorized subsets) into a multipolicy setting, and we present both a multi-policy distributed decryption scheme and a multi-policy distributed signature scheme. Additionally, we give a short outlook on how to apply the presented multi-secret sharing schemes in the design of other multi-policy cryptosystems, like the signcryption schemes considered in this thesis. For all the schemes proposed throughout the thesis, we follow the same formal structure. After de ning the protocols of the primitive and the corresponding security model, we propose the new scheme and formally prove its security, by showing a reduction to some computationally hard mathematical problem.

    Avui en dia les persones estan implicades cada dia més en diferents activitats digitals tant en la seva vida professional com en el seu temps lliure. Molts articles de paper, com diners i tiquets, estan sent reemplaçats més i més per objectes digitals. La criptografia juga un paper crucial en aquesta transformació, perquè proporciona seguretat en la comunicació entre els diferents participants que utilitzen un canal digital. Depenent de la situació específica, alguns requisits de seguretat en la comunicació poden incloure privacitat (o confidencialitat), autenticitat, integritat o no-repudi. En algunes situacions, repartir l'operació secreta entre un grup de participants fa el procés més segur i fiable que quan la informació secreta està centralitzada en un únic participant; la criptografia distribuïda és l’àrea de la criptografia que estudia aquestes situacions. Aquesta tesi tracta de primitives relacionades amb el camp de la criptografia distribuïda. Primer, estudiem esquemes “signcryption”, que ofereixen a la vegada les funcionalitats de xifrat i signatura, on l'operació de “unsigncryption” està distribuïda. Considerem aquesta primitiva des d’un punt de vista teòric i establim un marc de seguretat per ella. Llavors, presentem dos esquemes “signcryption” amb operació de “unsigncryption” determinada per una estructura llindar, cada un amb diferents propietats. A més, utilitzem la seva propietat d’autenticitat per desenvolupar una nova primitiva: signatures digitals amb verificació distribuïda. El segon bloc de la tesi tracta la primitiva dels esquemes de compartició de multi-secrets. Després de demostrar algunes limitacions en l’eficiència dels esquemes de compartició de multi-secrets en un escenari de teoria de la informació, presentem diversos esquemes de compartició de multi-secrets amb seguretat computacional demostrable. Finalment, utilitzem els resultats obtinguts en els esquemes de compartició de multi-secrets per generalitzar el paradigma tradicional de la criptografia distribuïda (amb una única política de subconjunts autoritzats) a un marc multi-política, i presentem un esquema de desxifrat distribuït amb multi-política i un esquema de signatura distribuïda amb multi-política. A més, donem indicacions de com es poden aplicar els nostres esquemes de compartició de multi-secrets en el disseny d’altres criptosistemes amb multi-política, com per exemple els esquemes “signcryption” considerats en aquesta tesi. Per tots els esquemes proposats al llarg d’aquesta tesi, seguim la mateixa estructura formal. Després de definir els protocols de la primitiva primitius i el model de seguretat corresponent, proposem el nou esquema i demostrem formalment la seva seguretat, mitjançant una reducció a algun problema matemàtic computacionalment difícil.

  • Foreword from the DPM 2012 program chairs

     Di Pietro, Roberto; Herranz Sotoca, Javier
    Lecture notes in computer science
    Vol. 7731, p. 5
    Date of publication: 2012-09-13
    Journal article

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  • More hybrid and secure protection of statistical data sets

     Herranz Sotoca, Javier; Nin Guerrero, Jordi; Solé Simó, Marc
    IEEE transactions on dependable and secure computing
    Vol. 9, num. 5, p. 727-740
    DOI: 10.1109/TDSC.2012.40
    Date of publication: 2012-09
    Journal article

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    Different methods and paradigms to protect data sets containing sensitive statistical information have been proposed and studied. The idea is to publish a perturbed version of the data set that does not leak confidential information, but that still allows users to obtain meaningful statistical values about the original data. The two main paradigms for data set protection are the classical one and the synthetic one. Recently, the possibility of combining the two paradigms, leading to a hybrid paradigm, has been considered. In this work, we first analyze the security of some synthetic and (partially) hybrid methods that have been proposed in the last years, and we conclude that they suffer from a high interval disclosure risk. We then propose the first fully hybrid SDC methods; unfortunately, they also suffer from a quite high interval disclosure risk. To mitigate this, we propose a postprocessing technique that can be applied to any data set protected with a synthetic method, with the goal of reducing its interval disclosure risk. We describe through the paper a set of experiments performed on reference data sets that support our claims

  • Attribute-based encryption schemes with constant-size ciphertexts

     Attrapadung, Nuttapong; Herranz Sotoca, Javier; Laguillaumie, Fabien; Libert, B.; de Panafieu, Elie; Rafols Salvador, Carla
    Theoretical computer science
    Vol. 422, p. 15-38
    DOI: 10.1016/j.tcs.2011.12.004
    Date of publication: 2012-03-09
    Journal article

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  • Kd-trees and the real disclosure risks of large statistical databases

     Herranz Sotoca, Javier; Nin Guerrero, Jordi; Solé Simó, Marc
    Information fusion
    Vol. 13, num. 4, p. 260-273
    DOI: 10.1016/j.inffus.2011.03.001
    Date of publication: 2012
    Journal article

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    In data privacy, record linkage can be used as an estimator of the disclosure risk of protected data. To model the worst case scenario one normally attempts to link records from the original data to the protected data. In this paper we introduce a parametrization of record linkage in terms of a weighted mean and its weights, and provide a supervised learning method to determine the optimum weights for the linkage process. That is, the parameters yielding a maximal record linkage between the protected and original data. We compare our method to standard record linkage with data from several protection methods widely used in statistical disclosure control, and study the results taking into account the performance in the linkage process, and its computational effort

  • Short attribute-based signatures for threshold predicates

     Herranz Sotoca, Javier; Laguillaumie, Fabien; Libert, B.; Rafols Salvador, Carla
    Cryptographers' Track at the RSA Conference
    p. 51-67
    DOI: 10.1007/978-3-642-27954-6_4
    Presentation's date: 2012
    Presentation of work at congresses

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    Cifrado homomorfico de clave publica basado en Residuosidad Cuadratica  Open access

     Herranz Sotoca, Javier; Sisternes, Juan Ramón
    Reunión Española sobre Criptología y Seguridad de la Información
    p. 1-6
    Presentation's date: 2012-09
    Presentation of work at congresses

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    Los esquemas de cifrado de clave p´ ublica con propiedades homom´orficas tienen muchas utilidades en aplicaciones reales. Entre los esquemas con propiedades homom´orficas aditivas existentes, hay una familia (desde el esquema de Goldwasser-Micali hasta el esquema de Paillier) cuya seguridad se basa en problemas computacionalmente dif´ıciles relacionados con el problema de factorizar un n´umero grande N. Los esquemas de esta familia tienen diferentes propiedades tanto en lo referente a la eficiencia, como al problema de teor´ıa de n´umeros concreto en el que basan su seguridad. En este art´ıculo proponemos un nuevo esquema a a˜nadir a esta familia. La hip´otesis computacional en la que se basa la seguridad de nuestro esquema es la hip´otesis de la Residuosidad Cuadr´atica m´odulo N. En t´erminos de eficiencia, por un lado nuestro esquema mejora todos los esquemas anteriores cuya seguridad se basa en la hip´otesis de la Residuosidad d-´esima m´odulo N, para d 2; por otro lado, nuestro esquema es en general menos eficiente (tiempo de descifrado) que algunos esquemas como el de Paillier, cuya seguridad se basa en otra hip´otesis (Residuosidad N-´esima m´odulo N2). Sin embargo, si los mensajes a cifrar son cortos, la eficiencia de nuestro esquema es esencialmente la misma que la del esquema de Paillier

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    Firmas digitales con verificación distribuida en el modelo de seguridad estándar  Open access

     Herranz Sotoca, Javier; Ruiz Rodriguez, Alexandre; Saez Moreno, German
    Reunión Española sobre Criptología y Seguridad de la Información
    p. 1-6
    Presentation's date: 2012-09
    Presentation of work at congresses

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    Las firmas digitales con verificaci´on distribuida protegen en cierta manera el nivel de anonimato o privacidad del firmante, ya que un subconjunto autorizado de usuarios deben colaboran para verificar la (in)validez de una firma. En trabajos anteriores se propusieron esquemas de este tipo pero que o no alcanzaban el nivel m´aximo de seguridad o bien lo hac´ıan en el modelo del or´aculo aleatorio. Proponemos aqu´ı el primer esquema de firma digital con verificaci´on distribuida que consigue seguridad m´axima, en t´erminos de infalsificabilidad y privacidad, y con seguridad demostrable en el modelo de computaci´on est´andar.

  • Identity-based encryption with master key-dependent message security and leakage-resilience

     Galindo, David; Herranz Sotoca, Javier; Villar Santos, Jorge Luis
    European Symposium on Research in Computer Security
    p. 627-642
    DOI: 10.1007/978-3-642-33167-1_36
    Presentation's date: 2012-09
    Presentation of work at congresses

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  • Attribute-based group key establishment

     Herranz Sotoca, Javier
    Mathematical reviews
    Date of publication: 2011
    Journal article

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  • New approaches for deniable authentication

     Herranz Sotoca, Javier
    Mathematical reviews
    Date of publication: 2011
    Journal article

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  • Any 2-asummable bipartite function is weighted threshold

     Herranz Sotoca, Javier
    Discrete applied mathematics
    Vol. 159, num. 11, p. 1079-1084
    DOI: 10.1016/j.dam.2011.01.023
    Date of publication: 2011-07-06
    Journal article

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  • Revocable attribute-based signatures with adaptive security in the standard model

     Escala Ribas, Alex; Herranz Sotoca, Javier; Morillo Bosch, Maria Paz
    Lecture notes in computer science
    Vol. 6737, p. 224-241
    Date of publication: 2011-05-10
    Journal article

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  • Restricted adaptive oblivious transfer

     Herranz Sotoca, Javier
    Theoretical computer science
    Vol. 412, num. 46, p. 6498-6506
    DOI: 10.1016/j.tcs.2011.06.023
    Date of publication: 2011-10-28
    Journal article

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    Optimal symbol alignment distance: a new distance for sequences of symbols  Open access

     Herranz Sotoca, Javier; Nin Guerrero, Jordi; Solé Simó, Marc
    IEEE transactions on knowledge and data engineering
    Vol. 23, num. 10, p. 1541-1554
    DOI: 10.1109/TKDE.2010.190
    Date of publication: 2011-10-14
    Journal article

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    Comparison functions for sequences (of symbols) are important components of many applications, for example clustering, data cleansing and integration. For years, many efforts have been made to improve the performance of such comparison functions. Improvements have been done either at the cost of reducing the accuracy of the comparison, or by compromising certain basic characteristics of the functions, such as the triangular inequality. In this paper, we propose a new distance for sequences of symbols (or strings) called Optimal Symbol Alignment distance (OSA distance, for short). This distance has a very low cost in practice, which makes it a suitable candidate for computing distances in applications with large amounts of (very long) sequences. After providing a mathematical proof that the OSA distance is a real distance, we present some experiments for different scenarios (DNA sequences, record linkage, ...), showing that the proposed distance outperforms, in terms of execution time and/or accuracy, other well-known comparison functions such as the Edit or Jaro-Winkler distances.

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  • Relations between semantic security and anonymity in identity based encryption

     Herranz Sotoca, Javier; Laguillaumie, Fabien; Rafols Salvador, Carla
    Information processing letters
    Vol. 11, num. 10, p. 453-460
    DOI: 10.1016/j.ipl.2011.02.002
    Date of publication: 2011
    Journal article

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  • Attribute-based signature with policy-and-endorsement mechanism

     Herranz Sotoca, Javier
    Mathematical reviews
    Date of publication: 2011
    Journal article

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  • Revocable attribute-based signatures with adaptive security in the standard model

     Escala Ribas, Alex; Herranz Sotoca, Javier; Morillo Bosch, Maria Paz
    International Conference on Cryptology in Africa
    p. 224-241
    Presentation's date: 2011-07-05
    Presentation of work at congresses

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  • Constant size ciphertexts in threshold attribute-based encryption

     Herranz Sotoca, Javier; Laguillaumie, Fabien; Rafols Salvador, Carla
    Lecture notes in computer science
    Vol. 6056, p. 19-34
    DOI: 10.1007/978-3-642-13013-7_2
    Date of publication: 2010
    Journal article

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  • Fully secure threshold unsigncryption

     Herranz Sotoca, Javier; Saez Moreno, German
    Lecture notes in computer science
    Vol. 6402, p. 261-278
    DOI: 10.1007/978-3-642-16280-0_18
    Date of publication: 2010-10-13
    Journal article

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  • On server trust in private proxy auctions

     Di Crescenzo, Giovanni; Herranz Sotoca, Javier; Saez Moreno, German
    Electronic commerce research
    Vol. 10, num. 3-4, p. 291-311
    DOI: 10.1007/s10660-010-9057-x
    Date of publication: 2010-10-09
    Journal article

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    We investigate proxy auctions, an auction model which is proving very successful for on-line businesses (e.g.http://www.ebay.com), where a trusted server manages bids from clients by continuously updating the current price of the item and the currently winning bid as well as keeping private the winning client’s maximum bid. We propose techniques for reducing the trust in the server by defining and achieving a security property, called server integrity. Informally, this property protects clients from a novel and large class of attacks from a corrupted server by allowing them to verify the correctness of updates to the current price and the currently winning bid. Our new auction scheme achieves server integrity and satisfies two important properties that are not enjoyed by previous work in the literature: it has minimal interaction, and only requires a single trusted server. The main ingredients of our scheme are two minimal-round implementations of zero-knowledge proofs for proving lower bounds on encrypted values: one based on discrete logarithms that is more efficient but uses the random oracle assumption, and another based on quadratic residuosity that only uses standard intractability assumptions but is less efficient.

  • Some (in)sufficient conditions for secure hybrid encryption

     Herranz Sotoca, Javier; Hofheinz, Dennis; Kiltz, Eike
    Information and computation
    Vol. 208, num. 11, p. 1243-1257
    DOI: 10.1016/j.ic.2010.07.002
    Date of publication: 2010
    Journal article

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  • Distributed privacy-preserving methods for statistical disclosure control

     Herranz Sotoca, Javier; Nin Guerrero, Jordi; Torra Raventós, Vicenç
    Lecture notes in computer science
    Vol. 5939, p. 33-47
    Date of publication: 2010
    Journal article

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    Statistical disclosure control (SDC) methods aim to protect privacy of the confidential information included in some databases, for example by perturbing the non-confidential parts of the original databases. Such methods are commonly used by statistical agencies before publishing the perturbed data, which must ensure privacy at the same time as it preserves as much as possible the statistical information of the original data. In this paper we consider the problem of designing distributed privacy-preserving versions of these perturbation methods: each part of the original database is owned by a different entity, and they want to jointly compute the perturbed version of the global database, without leaking any sensitive information on their individual parts of the original data. We show that some perturbation methods do not allow a private distributed extension, whereas other methods do. Among the methods that allow a distributed privacy-preserving version, we can list noise addition, resampling and a new protection method, rank shuffling, which is described and analyzed here for the first time.

  • On the generic construcion of identity-based signatures with additional properties

     Galindo, David; Herranz Sotoca, Javier; Kiltz, Eike
    Advances in mathematics
    Vol. 4, num. 4, p. 423-453
    DOI: 10.3934/amc.2010.4.453
    Date of publication: 2010-11
    Journal article

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  • CRIPTOGRAFIA DE CLAVE PUBLICA Y COMPARTICIÓN DE SECRETOS

     Morillo Bosch, Maria Paz; Gracia Rivas, Ignacio; Martí Farré, Jaume; Martin Mollevi, Sebastia; Padro Laimon, Carles; Saez Moreno, German; Herranz Sotoca, Javier; Rafols Salvador, Carla; Heidarvand, Somayed; Villar Santos, Jorge Luis
    Competitive project

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  • European Network of Excellence for Cryptology II

     Morillo Bosch, Maria Paz; Martí Farré, Jaume; Padro Laimon, Carles; Rafols Salvador, Carla; Gracia Rivas, Ignacio; Heidarvand, Somayed; Herranz Sotoca, Javier; Saez Moreno, German; Martin Mollevi, Sebastia; Villar Santos, Jorge Luis
    Competitive project

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  • Additively homomorphic encryption with d-operand multiplications

     Aguilar Melchor, Carlos; Gaborit, Philippe; Herranz Sotoca, Javier
    Lecture notes in computer science
    Vol. 6223, p. 138-154
    DOI: 10.1007/978-3-642-14623-7_8
    Date of publication: 2010
    Journal article

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    Classifying data from protected statistical datasets  Open access

     Herranz Sotoca, Javier; Matwin, Stan; Nin Guerrero, Jordi; Torra Raventós, Vicenç
    Computers and security
    Vol. 29, num. 8, p. 875-890
    DOI: 10.1016/j.cose.2010.05.005
    Date of publication: 2010-06-09
    Journal article

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    Statistical Disclosure Control (SDC) is an active research area in the recent years. The goal is to transform an original dataset X into a protected one X0, such that X0 does not reveal any relation between confidential and (quasi-)identifier attributes and such that X0 can be used to compute reliable statistical information about X. Many specific protection methods have been proposed and analyzed, with respect to the levels of privacy and utility that they offer. However, when measuring utility, only differences between the statistical values of X and X0 are considered. This would indicate that datasets protected by SDC methods can be used only for statistical purposes. We show in this paper that this is not the case, because a protected dataset X0 can be used to construct good classifiers for future data. To do so, we describe an extensive set of experiments that we have run with different SDC protection methods and different (real) datasets. In general, the resulting classifiers are very good, which is good news for both the SDC and the Privacy-preserving Data Mining communities. In particular, our results question the necessity of some specific protection methods that have appeared in the privacy-preserving data mining (PPDM) literature with the clear goal of providing good classification.

  • Extensions of access structures and their cryptographic applications

     Daza Fernandez, Vanesa; Herranz Sotoca, Javier; Morillo Bosch, Maria Paz; Rafols Salvador, Carla
    Applicable algebra in engineering communication and computing
    Vol. 21, num. 4, p. 257-284
    DOI: 10.1007/s00200-010-0125-1
    Date of publication: 2010-07
    Journal article

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  • Introduction to privacy and anonymity in information management systems

     Herranz Sotoca, Javier; Nin Guerrero, Jordi
    DOI: 10.1007/978-1-84996-238-4_1
    Date of publication: 2010-07-29
    Book chapter

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  • Constant size ciphertexts in threshold attribute-based encryption

     Herranz Sotoca, Javier; Laguillaumie, Fabien; Rafols Salvador, Carla
    International Conference on Practice and Theory in Public Key Cryptography
    p. 19-34
    DOI: 10.1007/978-3-642-13013-7_2
    Presentation's date: 2010-05-26
    Presentation of work at congresses

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  • Fully secure threshold unsigncryption

     Herranz Sotoca, Javier; Saez Moreno, German
    International Conference on Provable Security
    p. 261-278
    DOI: 10.1007/978-3-642-16280-0_18
    Presentation's date: 2010-10-14
    Presentation of work at congresses

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    Máxima seguridad para firmas digitales con verificación distribuida  Open access

     Herranz Sotoca, Javier; Ruiz Rodriguez, Alexandre; Saez Moreno, German
    Reunión Española sobre Criptología y Seguridad de la Información
    p. 150-162
    Presentation's date: 2010-09-10
    Presentation of work at congresses

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    Una de las opciones para proteger el nivel de anonimato o privacidad de un firmante es construir firmas digitales con verificación distribuida: se requiere la colaboración de un subconjunto autorizado de usuarios para verificar la (in)validez de una firma. En RECSI’08, se propuso un esquema de este tipo, pero que no alcanzaba el máximo nivel de seguridad. En este trabajo proponemos el primer esquema de firma digital con verificación distribuida que consigue seguridad máxima, en términos de infalsificabilidad y privacidad. Demostramos formalmente estas dos propiedades por reducción a problemas computacionales estándar, en el modelo del oráculo aleatorio.

    Postprint (author’s final draft)

  • Using classification methods to evaluate attribute disclosure risk

     Nin Guerrero, Jordi; Herranz Sotoca, Javier; Torra Raventós, Vicenç
    International Conference on Modeling Decisions for Artificial Intelligence
    p. 277-286
    DOI: 10.1007/978-3-642-16292-3_27
    Presentation's date: 2010-10-29
    Presentation of work at congresses

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  • On the transferability of private signatures

     Herranz Sotoca, Javier
    Information sciences
    Vol. 179, num. 11, p. 1647-1656
    Date of publication: 2009-05
    Journal article

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  • The Kurosawa-Desmedt key encapsulation is not chosen-ciphertext secure

     Choi, SG; Herranz Sotoca, Javier; Hofheinz, D; Hwang, JY; Kiltz, E; Lee, DH; Yung, M
    Information processing letters
    Vol. 109, num. 16, p. 897-901
    DOI: 10.1016/j.ipl.2009.04.007
    Date of publication: 2009-07
    Journal article

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    Ideal homogeneous access structures constructed from graphs  Open access

     Herranz Sotoca, Javier
    Journal of universal computer science
    Vol. 15, num. 14, p. 2881-2893
    DOI: 10.3217/jucs-015-14-2881
    Date of publication: 2009
    Journal article

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    Starting from a new relation between graphs and secret sharing schemes introduced by Xiao, Liu and Zhang, we show a method to construct more general ideal homogeneous access structures. The method has some advantages: it efficiently gives an ideal homogeneous access structure for the desired rank, and some conditions can be imposed (such as forbidden or necessary subsets of players), even if the exact composition of the resulting access structure cannot be fully controlled. The number of homogeneous access structures that can be constructed in this way is quite limited; for example, we show that (t, l)-threshold access structures can be constructed from a graph only when t = 1, t = l - 1 or t = l.

  • Partial symbol ordering distance

     Herranz Sotoca, Javier; Nin Guerrero, Jordi
    Lecture notes in computer science
    Vol. 5861, p. 293-302
    DOI: 10.1007/978-3-642-04820-3_27
    Date of publication: 2009
    Journal article

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  • Flaws in some self-healing key distribution schemes with revocation

     Daza Fernandez, Vanesa; Herranz Sotoca, Javier; Saez Moreno, German
    Information processing letters
    Vol. 109, num. 11, p. 523-526
    Date of publication: 2009-05
    Journal article

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  • A new algorithm to search for small nonzero |x^3 - y^2| values

     Jiménez, I; Herranz Sotoca, Javier; Saez Moreno, German
    Mathematics of computation
    Vol. 5545, p. 770-779
    DOI: 10.1090/S0025-5718-09-02240-6
    Date of publication: 2009-01
    Journal article

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  • Distributed privacy-preserving methods for statistical disclosure control

     Herranz Sotoca, Javier; Nin Guerrero, Jordi; Torra Raventós, Vicenç
    International Workshop on Data Privacy Management
    p. 33-47
    DOI: 10.1007/978-3-642-11207-2_4
    Presentation's date: 2009-09-23
    Presentation of work at congresses

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  • Partial symbol ordering distance

     Herranz Sotoca, Javier; Nin Guerrero, Jordi
    International Conference on Modeling Decisions for Artificial Intelligence
    p. 293-302
    DOI: 10.1007/978-3-642-04820-3_27
    Presentation's date: 2009-12
    Presentation of work at congresses

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    Nowadays sequences of symbols are becoming more important, as they are the standard format for representing information in a large variety of domains such as ontologies, sequential patterns or non numerical attributes in databases. Therefore, the development of new distances for this kind of data is a crucial need. Recently, many similarity functions have been proposed for managing sequences of symbols; however, such functions do not always hold the triangular inequality. This property is a mandatory requirement in many data mining algorithms like clustering or k-nearest neighbors algorithms, where the presence of a metric space is a must. In this paper, we propose a new distance for sequences of (non-repeated) symbols based on the partial distances between the positions of the common symbols. We prove that this Partial Symbol Ordering distance satisfies the triangular inequality property, and we finally describe a set of experiments supporting that the new distance outperforms the Edit distance in those ecenarios where sequence similarity is related to the positions occupied by the symbols.

  • Access to the full text
    A cryptographic solution for private distributed simple meeting scheduling  Open access

     Herranz Sotoca, Javier; Matwin, Stan; Meseguer González, Pedro; Nin Guerrero, Jordi
    International Conference of the Catalan Association for Artificial Intelligence
    p. 275-283
    DOI: 10.3233/978-1-60750-061-2-275
    Presentation's date: 2009
    Presentation of work at congresses

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    Meeting scheduling is a suitable application for distributed computation motivated by its privacy requirements. Previous work on this problem have considered some cryptographic and conceptually clear approach to solve a simple case of Meeting Scheduling, even achieving complete privacy.

  • Ad-hoc threshold broadcast encryption with shorter ciphertexts

     Daza Fernandez, Vanesa; Herranz Sotoca, Javier; Morillo Bosch, Maria Paz; Rafols Salvador, Carla
    Electronic notes in theoretical computer science
    Vol. 192, num. 2, p. 3-15
    Date of publication: 2008-05
    Journal article

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