Prophet: A Context-Aware Location Privacy-Preserving Scheme in Location Sharing Service

Algorithm 1

Building the ASR.

INPUT:  // anonymity parameters

     // information availability parameters

     // user’s exact location

     // the Hilbert threaded regions

OUTPUT:  // anonymous space region

BuildASR

(1) ;

// Step (1)

(2) ;

(3)  ();

(4) 

(5)   num++;

(6)   ;

(7) while  ;

(8) for  ; ++;   do

(9)   for  ; ++;   do

(10)    ;

(11) for each   in   do // Step (2)

(12)  if then

(13)   record the correspond POIs and into ;

(14) delete POIs of from Loc;

(15) ();

(16) jump to Step (1);

  // Step (3)

(17) find the points , from ;

(18) compute the area of ASR (, );

(19) if    then

(20)  delete POIs corresponding with , ;

(21) ();

(22) jump to Step (1);

(23) return ASR;