An Improved Privacy-Preserving Framework for Location-Based Services Based on Double Cloaking Regions with Supplementary Information Constraints

Algorithm 1

DMA (dynamic matching algorithm).

Input: Privacy protection level , User’s grid ID GID

Output: Double Cloaking Region (RCR and FCR)

Anonymizer selects the spatial hierarchy according to the privacy protection level h

Randomly match the user’s grid into a grid region

for query count in

 if query count≠0 then

  add query count to Sets

 end if

end for

The Sets are randomly divided into and equally

Do

   = average(); = average();

  for in Sets

   if then

     belong to

   else

     belong to

   end if

  end for

while there are changes on the elements in and

if the number of GID belongs to then

  FCR isselected randomly from the regions with the number in except RCR

else FCR is selected randomly from the regions with the number in except RCR

end if

return FCR and RCR