| Input: |
| DSetloc (The personal request location set), k (The privacy level), T (The semantic tree), qreal (The historical query probability of the requested location), DSetloc (Historical query probability set), ∂ (Query probability threshold), RL (Real Location of request user); |
| Output: |
| Anonymity set, AS; |
| 1: Computing the query probability of each locations and establish DSetloc; |
| STEP1: Choose the location that satisfies the constraints of query probability to built ACS |
| 2: Initialize the anonymous candidate set ACS=RL; |
| 3: while Len (ACS)<2k do |
| 4: for Each loc in DSetloc and Each q in DSetque do |
| 5: Compting the dque (q, qreal) by formula (6) |
| 6: if dque (q, qreal) < ∂then |
| 7: Put loc into ACS; |
| 8: end if |
| 9: end for |
| 10: end while |
| STEP2: Choose the location that satisfies the constraints of minimum semantic difference and semantic diversity to built AS |
| 11: Initialize the anonymous set AS=RL; |
| 12: According to personal semantic tree T and formula (3), semantic distance matrix SDM is established; |
| 13: while Len (AS)<kdo |
| 14: if Len (ACS)==0 then |
| 15: Anonymity Failure; |
| 16: else |
| 17: Computing the SDE−(loc); |
| 18: for Each loc in ACS do |
| 19: Computing the SDE+(loc) and dsde (loc) by formulate (5); |
| 20: if SDM (index (loc), index (RL))>6 and dsde (loc) > qthen |
| 21: Put loc into AS; |
| 22: end if |
| 23: end for |
| 24: end if |
| STEP3: Replace some locations to improve security |
| 25: Replace some anonymous locations in AS with similar semantic feature from other users; |
| 26: end while |
| 27: return AS; |
