A Privacy-Preserving Location-Based System for Continuous Spatial Queries

Algorithm 2

Anonymizer’s query processing.

Input: query issuer’s current location and destination, CR chosen by the query issuer, and (number of clients for location

anonymity), content of the query

Output: K-anonymous clients in a minimum CR, member clients

() Check the CR chosen by the query issuer using the anonymizer;

() Calculate the minimum distance (, , , = null);

() if    then return 0

()  

()  while  

()   

()   ;

()   ;

()    if ();

()      continuous;

()     else end if;

()   end while;

() if (periodically measure the CRs of dist(, ) and sort the CRs in ascending order (i.e., from the smallest to the largest))

() return  ; (th is from 1 to )