With the advance of location technologies, people can now determine their location in various way... more 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. Namely, we suggest having multiple brokers, each deployed by a different organization (e.g., an operator of a cellph...
2009 IEEE International Conference on Pervasive Computing and Communications, 2009
To benefit from a location-based service, a person must reveal her location to the service. Howev... more To benefit from a location-based service, a person must reveal her location to the service. However, knowing the person's location might allow the service to re-identify the person. Location privacy based on k-anonymity addresses this threat by cloaking the person's location such that there are at least k − 1 other people within the cloaked area and by revealing only the cloaked area to a location-based service. Previous research has explored two ways of cloaking: First, have a central server that knows everybody's location determine the cloaked area. However, this server needs to be trusted by all users and is a single point of failure. Second, have users jointly determine the cloaked area. However, this approach requires that all users trust each other, which will likely not hold in practice. We propose a distributed approach that does not have these drawbacks. Our approach assumes that there are multiple servers, each deployed by a different organization. A user's location is known to only one of the servers (e.g., to her cellphone provider), and different users let different servers (cellphone providers) know of their location. With the help of cryptography, the servers and a user jointly determine whether the k-anonymity property holds for the user's area, without the servers learning any additional information, not even whether the property holds. A user learns whether the k-anonymity property is satisfied, but no other information. The evaluation of our sample implementation shows that our distributed k-anonymity protocol is sufficiently fast to be practical. Moreover, our protocol integrates well with existing infrastructures for locationbased services, as opposed to the previous research.
Centre for Applied Cryptographic Research ( …, 2007
The Advanced Access Content System (AACS) is a content distribution system for record-able and pr... more The Advanced Access Content System (AACS) is a content distribution system for record-able and pre-recorded media, currently used to protect HD-DVD and Blu-Ray content. AACS builds off of its predecessors, the Content Scramble System (CSS) and ...
Location privacy is of utmost concern for location-based services. It is the property that a pers... more Location privacy is of utmost concern for location-based services. It is the property that a person's location is revealed to other entities, such as a service provider or the person's friends, only if this release is strictly necessary and authorized by the person. We study how to achieve location privacy for a service that alerts people of nearby friends. Here, location privacy guarantees that users of the service can learn a friend's location if and only if the friend is actually nearby. We introduce three protocols-Louis, Lester and Pierre-that provide location privacy for such a service. The key advantage of our protocols is that they are distributed and do not require a separate service provider that is aware of people's locations. The evaluation of our sample implementation demonstrates that the protocols are sufficiently fast to be practical.
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Papers by Ge Zhong