Database Reference
In-Depth Information
Many applications may require only
aggregate
information col-
lected by the sensors, rather than exact information about indi-
viduals. For example, tra
c conditions in a vehicular sensing ap-
plications can be inferred with the use of aggregate data. Examples
of systems which use aggregate data for privacy-preserving queries
in smart vehicular sensing environments are discussed in [87].
A variety of privacy-preservation mechanisms such as
k
-anonymity,
-diversity, and
t
-closeness reduce the accuracy of the data before
sharing it with other entities [10]. For example, for video data, the
faces in the videos can be blurred in order to reduce the likelihood
of identification [112]. In the context of mobile and location data, a
variety of methods such as spatial cloaking, spatial delays, adding
noise to locations etc. [29, 8] are incorporated in order to increase
data privacy. A detailed discussion of methods for increasing lo-
cation privacy are provided in [8].
In practice, it is desirable to set up a set of policies which can allow users
to specify which kinds of data they would like to share about themselves.
The W3C group has defined the
Platform for Privacy Preferences (P3P)
[125], which provides a language for description of privacy preferences.
This allows the user to set specific privacy requirements, and also allows
for automatic negotiation between the personal information needs of a
user and their privacy preferences.
The issue of privacy has also been addressed in the context of the se-
mantic web [38, 64]. The broad idea in [38] is that users are able to retain
control over who has access to their personal information under different
conditions. For instance, one may allow their colleagues to access their
calender over the weekend, but not over weekdays. In addition, it is
desirable to fine tune the granularity of the query responses, depending
upon the identity of the person who is performing the queries. A seman-
tic web architecture is proposed in [38], which supports the automated
discovery and access of personal resources for a variety of context-aware
applications. Each source of contextual information (e.g. a calendar,
location tracking functionality, collections of relevant user preferences,
organizational databases) is represented as a semantic web service. A
semantic e-Wallet acts as a directory of contextual resources for a given
user, while enforcing her privacy preferences. Privacy preferences enable
users to specify what information can be provided to whom in different
contexts. They also allow users to specify
obfuscation rules
, which con-
trol the accuracy or inaccuracy of the information provided in response
to different queries under different conditions.
