The increasing availability of location-aware mobile devices
has given rise to a flurry of location-based services (LBS). Due to the
nature of spatial queries, an LBS needs the user position in order to pro-
cess her requests. On the other hand, revealing exact user locations to a
(potentially untrusted) LBS may pinpoint their identities and breach their
privacy. To address this issue, spatial anonymity techniques obfuscate
user locations, forwarding to the LBS a sufficiently large region instead.
Existing methods explicitly target processing in the Euclidean space,
and do not apply when proximity to the users is defined according to
network distance (e.g., driving time through the roads of a city). In this
paper, we propose a framework for anonymous query processing in road
networks. We design location obfuscation techniques that (i) provide
anonymous LBS access to the users, and (ii) allow efficient query
processing at the LBS side. Our techniques exploit existing network
database infrastructure, requiring no specialized storage schemes or
functionalities. We experimentally compare alternative designs in real
road networks and demonstrate the effectiveness of our techniques.