With the advance of location technologies, people can now
determine their location in various ways, for instance, with GPS or based
on nearby cellphone towers. These technologies have led to the
introduction of location-based services, which allow people to get
information relevant to their current location. Location privacy is of
utmost concern for such location-based services, since knowing a person's
location can reveal information about her activities or her interests.
In this thesis, we first focus on location-based services that need to
know only a person's location, but not her identity. We propose a solution
using location cloaking based on k-anonymity, which requires neither a
single trusted location broker, which is a central server that knows
everybody's location, nor trust in all users of the system and that
integrates nicely with existing infrastructures. We present two such
protocols. The evaluation of our sample implementation demonstrates that
one of the protocol is sufficiently fast to be practical, but the
performance of the other protocol is not acceptable for its use in
practice.
In addition to the distributed k-anonymity protocol we then propose four
protocols---Louis, Lester, Pierre and Wilfrid--- for a specific, identity
required, location-based service: the nearby-friend application, where
users (and their devices) can learn information about their friends'
location if and only if their friends are actually nearby. Our solutions
do not require any central trusted server or only require a semi-trusted
third party that dose not learn any location information. Moreover, users
of our protocol do not need to be members of the same cellphone provider,
as in existing approaches. The evaluation on our implementation shows that
all of the four protocols are efficient
