A Context-Aware Location Differential Perturbation Scheme for Privacy-Aware Users in Mobile Environment

Algorithm 1

Modified Hilbert curve construction algorithm.

Input:ℛ as the (rectangle) boundary of the map, Ψ as the set of all POIs in the map

Output: a quad-tree root node T

if in ℛ is great than pre-determined threshold σ, then

partition ℛ equally into four sub-cells ℛ_nw, ℛ_ne, ℛ_se, ℛ_sw;

for i=nw, ne, se, sw do

return 0 //recursively partition ℛ_i according to the condition >σ;

end for

else

return 1 //outputs quad-tree root node T;

end if