Combinatorial group testing, given a set C of individuals ("customers"), consists of applying group tests on subsets of C for the purpose of identifying which members of C are infected (or, more generally, defective in some way). The outcome of a group test reveals only the presence or absence of infection(s) in that group, but a number of group tests exactly identifies all infected members.

In the third-party model for the distribution of data, the trusted data creator or owner provides an untrusted party V with data and integrity verification (IV) items for that data. When a user U gets a subset of the data at D or is already in possession of that subset, U may request from D the IV items that make it possible for U to verify the integrity of its data: D must then provide U with the (hopefully small) number of needed IVs. Most of the published work in this area uses the Merkle tree or variants thereof. For the problem of 2-dimensional range data, the best published solutions require V to store O(n log n) IV items for a database of n items, and allow a user IA to be sent only O(log n) of those IVs for the purpose of verifying the integrity of the data it receives from D (regardless of the size of lA's query rectangle). For data that is modeled as a 2-dimensional grid (such as GIS or image data), this paper shows that better bounds are possible: The number of IVs stored at D (and the time it takes to compute them) can be brought down to O(n), and the number of IVs sent to IA for verification can be brought down to a constant.

Location-based service provisioning is of great interests to wireless Internet service providers (WISPs) to deliver attractive value-added services, such as service advertisements, product marketing, to the special network users according to their geographic coordinates, along with Internet access benefits. It is usually the case that the basic location information is derived from direct interactions between the infrastructure network and the wireless mobile devices. Unfortunately, the Internet access service easily becomes the target of free-riders and attackers by exploiting the location authentication protocols, and collusively forging their location claims. We propose a location authentication and authorization protocol, LBAC (location-based network access control), to securely authenticate the location claims of mobile wireless users, and to securely distribute the shared keys for data encryption purposes. In LBAC, location areas are defined by the shared points of multiple wireless access points. The fact that a mobile node is located at certain places is authenticated by the mobile node collecting all the key information from the corresponding access points. Using Diffie-Hellman algorithm, LBAC authenticates location claims, and derives the keys for each mobile node and access point pair. LBAC eliminates the dependence on global positioning system (GPS) or ultrasonic devices in order to localize the mobile devices. We enumerate possible attacks to the system and analyze their countermeasures. The computational, communicational and the memory requirement are also evaluated

With the proliferation of wireless communication technologies and mobile computing devices, research interest has grown for location-aware systems and services. We propose LAAC, a novel location-aware access control protocol based on a coarsely defined location area that is enclosed by overlapping areas of multiple access points. Accordingly, a location key for location claim is derived from the overlapping access points' beacon information. In addition, the fact that a mobile device derives the location key enables us to track the location of the mobile device. LAAC does not require additional hardwares such as GPS or ultrasonic devices in order to localize the mobile devices. We enumerate possible attacks to the system and analyze their countermeasures. The computational and communicational costs and the memory requirement are evaluated, and the simulation results are presented