Protecting Check-In Data Privacy in Blockchain Transactions with Preserving High Trajectory Pattern Utility

Algorithm 2

The Markov-chain location type recommendation algorithm.

Input: trajectory pattern matrix M, reverse trajectory pattern matrix R(M), sensitive sub-trajectory type = {}, recommended location type quantity threshold s;

Output: set T of location types.

1. Initialize T[i], i;

2. if ([0] ==) then

3. T[i]=,;

4. else if ([2] ==) then

5.  T[i]=,;

6. else then

7.  T[i]=; ;

8. sort(T[i]);

9. Select the first s location types with higher probability values and put them into T;

10. Return T.