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A Dummy-based Anonymization Method Based on User Trajectory with Pauses

A Dummy-based Anonymization Method Based on User Trajectory with Pauses. Ryo Kato, Mayu Iwata, Takahiro Hara, Akiyoshi Suzuki, Shojiro Nishio Osaka University Yuki Arase, Xing Xie Microsoft Research Asia ACM SIGSPATIAL GIS 2012. Overview. Location privacy in LBS

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A Dummy-based Anonymization Method Based on User Trajectory with Pauses

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  1. A Dummy-based Anonymization Method Based on User Trajectory with Pauses Ryo Kato, Mayu Iwata, Takahiro Hara, Akiyoshi Suzuki, ShojiroNishio Osaka University Yuki Arase, Xing Xie Microsoft Research Asia ACM SIGSPATIAL GIS 2012

  2. Overview • Location privacy in LBS • Extending k-Anonymous algorithm • Does not need a trusted third-party server User 1 User 1 User 1 k requests User 1 User 1 User 2 K-Anonymous server LBS provider User 1 User 1 User 3 User 1 User 1 User 4 k responses Actual location + dummy locations

  3. Related Work • [12] • Moving in a neighborhood • Moving in a limited neighborhood • [14] • Circle-based dummy • Uniform grid-based dummy • [18] • Location Traceable Tree(LT-tree)

  4. Dummy-based Approach

  5. Restrictions in Real World Environment • Consistency of movements • Consider actual road map information in order to generate reasonable dummy trajectories • Traceability • Anonymous area

  6. Proposed Approach - Assumptions • User continuously sends location to LBS provider • Moving with some distribution of speed • Stopping at several locations for a certain time • Movement plans are known in advance

  7. Proposed Approach Three Steps • Determine base pause position and base pause start time • Determine sets of shared pause positions and shared pause start times • Determine dummy’s movements

  8. Determining Base Pause Position and Base Pause Start Time 0 1 2 5 3 4 6 7 8 Base pause grid: 3 Base pause start time: 20s

  9. Determining Sets of Shared Pause Positions and Shared Paused Start Times Base pause position & Base pause start time Reachable Reachable Reachable

  10. Determining Dummy’s Movements Shared pause position T=3 Reachable Mid-pause position T=9 T=19 Mid-pause position T=14 Shared pause position T=28 T=22 T=12 Base pause position Shared pause position Mid-pause position

  11. Evaluation Setup • Network simulator MobiREAL

  12. Evaluation Metrics • Anonymous Area Achieving Ratio-Count(AAAR-Count) • Anonymous Area Achieving Ratio-Size(AAAR-Size) • Mean Time to Confusion(MTC)

  13. Methods Comparison • Previous method [17] • Similar method without pauses • Proposed method • Proposed method (AAAR-80) • Size of anonymous area varies greatly, low AAAR-Count found in some situations • Dynamically adjust anonymous area size to achieve 80% AAAR-Count

  14. Result – AAAR-Count

  15. Result – AAAR-Ratio

  16. Result – AAAR-80

  17. Result – MTC

  18. Conclusion & Future Work • The proposed approach generated dummies that moved naturally • Real world restrictions taken into consideration • Reactive dummies, does not need to know user’s movement plan in advance • Real world experiment with real humans

  19. Comments • Did not mention communication and computation cost • Prefer distribution/CDF plot over AAAR-Count/AAAR-Size percentage plot • No additional third-party server is required • Location accuracy is preserved

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