The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Practical Privacy Enhancing Technologies for Mobile Systems

Janne Lindqvist

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Information and Natural Sciences for public examination and debate in Auditorium T2 at Helsinki University of Technology (Espoo, Finland) on the 5th of June, 2009, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9903-4)   [476 KB]
Dissertation is also available in print (ISBN 978-951-22-9902-7)

Abstract

Mobile computers and handheld devices can be used today to connect to services available on the Internet. One of the predominant technologies in this respect for wireless Internet connection is the IEEE 802.11 family of WLAN standards. In many countries, WLAN access can be considered ubiquitous; there is a hotspot available almost anywhere. Unfortunately, the convenience provided by wireless Internet access has many privacy tradeoffs that are not obvious to mobile computer users. In this thesis, we investigate the lack of privacy of mobile computer users, and propose practical enhancements to increase the privacy of these users.

We show how explicit information related to the users' identity leaks on all layers of the protocol stack. Even before an IP address is configured, the mobile computer may have already leaked their affiliation and other details to the local network as the WLAN interface openly broadcasts the networks that the user has visited. Free services that require authentication or provide personalization, such as online social networks, instant messengers, or web stores, all leak the user's identity. All this information, and much more, is available to a local passive observer using a mobile computer.

In addition to a systematic analysis of privacy leaks, we have proposed four complementary privacy protection mechanisms. The main design guidelines for the mechanisms have been deployability and the introduction of minimal changes to user experience. More specifically, we mitigate privacy problems introduced by the standard WLAN access point discovery by designing a privacy-preserving access-point discovery protocol, show how a mobility management protocol can be used to protect privacy, and how leaks on all layers of the stack can be reduced by network location awareness and protocol stack virtualization. These practical technologies can be used in designing a privacy-preserving mobile system or can be retrofitted to current systems.

This thesis consists of an overview and of the following 4 publications:

  1. Janne Lindqvist and Laura Takkinen. 2006. Privacy management for secure mobility. In: Ari Juels and Marianne Winslett (editors). Proceedings of the 5th ACM Workshop on Privacy in the Electronic Society (WPES 2006). Alexandria, Virginia, USA. 30 October 2006.
  2. Tuomas Aura, Janne Lindqvist, Michael Roe, and Anish Mohammed. 2008. Chattering laptops. In: Nikita Borisov and Ian Goldberg (editors). Proceedings of the 8th Privacy Enhancing Technologies Symposium (PETS 2008). Leuven, Belgium. 23-25 July 2008. Springer. Lecture Notes in Computer Science, volume 5134, pages 167-186. © 2008 by authors.
  3. Janne Lindqvist and Juha-Matti Tapio. 2008. Protecting privacy with protocol stack virtualization. In: Vijay Atluri and Marianne Winslett (editors). Proceedings of the 7th ACM Workshop on Privacy in the Electronic Society (WPES 2008). Alexandria, Virginia, USA. 27 October 2008.
  4. Janne Lindqvist, Tuomas Aura, George Danezis, Teemu Koponen, Annu Myllyniemi, Jussi Mäki, and Michael Roe. 2009. Privacy-preserving 802.11 access-point discovery. Cambridge, United Kingdom. Microsoft Research Technical Report, MSR-TR-2009-7. An abridged version of this article is available in: David Basin, Srdjan Capkun, and Wenke Lee (editors). Proceedings of the Second ACM Conference on Wireless Network Security (WiSec 2009). Zürich, Switzerland. 16-18 March 2009, pages 123-130. © 2009 by authors.

Keywords: privacy, mobile systems, IEEE 802.11, anonymity, wireless networks

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© 2009 Helsinki University of Technology

Last update 2011-05-26