Table of Contents
International Journal of Vehicular Technology
Volume 2011, Article ID 486975, 12 pages
Research Article

Time in Privacy Preserving LBSs: An Overlooked Dimension

1Dipartimento di Informatica, Sapienza Università di Roma 00185, Roma, Italy
2Dipartimento di Matematica, Università di Roma Tre, Roma, Italy
3Dipartimento di Ingegneria e Scienza dell'Informazione, Università di Trento 38122, Trento, Italy
4Department of Computer Science, Vrije Universiteit Amsterdam, 1081 Amsterdam HV, The Netherlands

Received 16 October 2010; Revised 23 January 2011; Accepted 27 January 2011

Academic Editor: Cristina Pinotti

Copyright © 2011 Luciana Marconi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A new privacy model for Location-Based Services (LBSs) has been recently proposed based on users' footprints-these being a repre-sentation of the amount of time a user spends in a given area. Unfortunately, while the model is claimed to be independent from the specific knowledge of the adversary about users' footprints, we argue that an adversary, that has a more structured knowledge over time, can pose a threat to the privacy guarantees of the model. The major contribution of this paper is to show that time is a relevant dimension that needs to be taken into consideration when investigating LBSs privacy issues. In particular, we show that applying our considerations, user privacy can be violated. We support our claim with analysis and a concrete example. Furthermore, by analyzing a real data set of vehicular traces, we show that the threat is actually present in a real scenario and that its effect on jeopardizing user privacy is relevant.