Private Queries in Location-Based Services: Anonymizers are Not Necessary. Location-Based Services (LBS). LBS users Mobile devices with GPS capabilities Queries NN Queries Location server is NOT trusted. “Find closest hospital to my present location”. Problem Statement.
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“Find closest hospital to my present location”
NOT SECURE !!!
[Mok06] – Mokbel et al, The New Casper: Query Processing for Location Services without Compromising Privacy, VLDB 2006
[KGMP07] – Kalnis P., Ghinita G., Mouratidis K., Papadias D., "Preventing Location-Based Identity Inference in Anonymous Spatial Queries", IEEE TKDE 2007.
[CM07] C.-Y. Chow and M. Mokbel “Enabling Private Continuous Queries For Revealed User Locations”. In Proc. of SSTD 2007
[KS07] A. Khoshgozaran, C. Shahabi. Blind Evaluation of Nearest Neighbor Queries Using Space Transformation to Preserve Location Privacy , In Proc. Of SSTD 2007
QR * QR = QR
QR * QNR = QNR
bPIR Protocol for Binary Data
y1 y2 y3 y4
z2=QNR => X10=1
z2=QR => X10=0
uApproximate Nearest Neighbor
uExact Nearest Neighbor
A3: p1, p2, p3
A4: p1, --, --
Y1 Y2 Y3 Y4