Upload
beatriz-arwood
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
A Dummy-based Anonymization Method Based on User Trajectory with Pauses
Ryo Kato, Mayu Iwata, Takahiro Hara, Akiyoshi Suzuki, Shojiro Nishio
Osaka UniversityYuki Arase, Xing Xie
Microsoft Research AsiaACM SIGSPATIAL GIS 2012
User 1User 1
User 1User 1
User 1User 1
User 1User 1
Overview
• Location privacy in LBS• Extending k-Anonymous algorithm• Does not need a trusted third-party server
K-Anonymousserver
User 1
User 2
User 3
User 4
LBSprovider
k requests
k responsesActual location + dummy locations
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)
Restrictions in Real World Environment
• Consistency of movements– Consider actual road map information in order to
generate reasonable dummy trajectories• Traceability • Anonymous area
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
Proposed Approach
Three Steps1. Determine base pause position and base
pause start time2. Determine sets of shared pause positions and
shared pause start times3. Determine dummy’s movements
Determining Base Pause Position and Base Pause Start Time
0 1 2
3 4 5
6 7 8
T 0 1 2 3 … 8
0s 2 1 2 0 1
10s 1 3 0 1 2
20s 2 4 1 0 1
30s 0 0 3 0 1
total 5 8 6 1 5
Base pause grid: 3Base pause start time: 20s
Determining Sets of Shared Pause Positions and Shared Paused Start Times
Reachable
Reachable
Base pause position&
Base pause start time
Reachable
Determining Dummy’s Movements
T=3
T=12
T=14T=28
Reachable
Mid-pauseposition
Mid-pauseposition
Shared pauseposition
Shared pauseposition
Shared pauseposition
Base pauseposition
Mid-pauseposition T=9 T=19
T=22
Evaluation Metrics
• Anonymous Area Achieving Ratio-Count(AAAR-Count)
• Anonymous Area Achieving Ratio-Size(AAAR-Size)
• Mean Time to Confusion(MTC)
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
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