arXiv subjects

Claudio Bettini

Publications and source records attributed to Claudio Bettini.

21 records · Page 2Linked to original sources

arXiv2010

Privacy in geo-social networks: proximity notification with untrusted service providers and curious buddies

A major feature of the emerging geo-social networks is the ability to notify a user when one of his friends (also called buddies) happens to be geographically in proximity with the user. This proximity service is usually offered by the network itself or by a third party service provider (SP) using location data acquired from the users. This paper provides a rigorous theoretical and experimental analysis of the existing solutions for the location privacy problem in proximity services. This is a serious problem for users who do not trust the SP to handle their location data, and would only like to release their location information in a generalized form to participating buddies. The paper presents two new protocols providing complete privacy with respect to the SP, and controllable privacy with respect to the buddies. The analytical and experimental analysis of the protocols takes into account privacy, service precision, and computation and communication costs, showing the superiority of the new protocols compared to those appeared in the literature to date. The proposed protocols have also been tested in a full system implementation of the proximity service.

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arXiv2010

Preserving Privacy in Sequential Data Release against Background Knowledge Attacks

A large amount of transaction data containing associations between individuals and sensitive information flows everyday into data stores. Examples include web queries, credit card transactions, medical exam records, transit database records. The serial release of these data to partner institutions or data analysis centers is a common situation. In this paper we show that, in most domains, correlations among sensitive values associated to the same individuals in different releases can be easily mined, and used to violate users' privacy by adversaries observing multiple data releases. We provide a formal model for privacy attacks based on this sequential background knowledge, as well as on background knowledge on the probability distribution of sensitive values over different individuals. We show how sequential background knowledge can be actually obtained by an adversary, and used to identify with high confidence the sensitive values associated with an individual. A defense algorithm based on Jensen-Shannon divergence is proposed, and extensive experiments show the superiority of the proposed technique with respect to other applicable solutions. To the best of our knowledge, this is the first work that systematically investigates the role of sequential background knowledge in serial release of transaction data.

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arXiv2006

The Role of Quasi-identifiers in k-Anonymity Revisited

The concept of k-anonymity, used in the recent literature to formally evaluate the privacy preservation of published tables, was introduced based on the notion of quasi-identifiers (or QI for short). The process of obtaining k-anonymity for a given private table is first to recognize the QIs in the table, and then to anonymize the QI values, the latter being called k-anonymization. While k-anonymization is usually rigorously validated by the authors, the definition of QI remains mostly informal, and different authors seem to have different interpretations of the concept of QI. The purpose of this paper is to provide a formal underpinning of QI and examine the correctness and incorrectness of various interpretations of QI in our formal framework. We observe that in cases where the concept has been used correctly, its application has been conservative; this note provides a formal understanding of the conservative nature in such cases.

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