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UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Preserving Location Privacy on the Release of Large-scale
Mobility Data
Xueheng Hu, Aaron D. StriegelDepartment of Computer Science and Engineering
University of Notre Dame
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
IntroductionMobility models for wireless networks simulation
Synthetic models:• Easy to set up• Inadequate semantics to capture reality
Traces: • Observed in real life, expected to be accurate• Expensive to collect, privacy concerns
Challenge: trace publishing vs. location privacy
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
PreviewTrade-off: data utility vs. user privacy
Simulation scenariosDTN, Opportunistic N/W, etc.
Focusing on realistic wireless interactions - utilityFreeing from absolute locations - privacy
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Computational Efforts• Anonymization
Creating ambiguity, e.g. k-anonymity (Sweeney, 2002)
User A User B
User CUser A, B, and
C
Anonymization
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Computational Efforts• Obfuscation
Degrading data quality (Krumm, 2009)
(a) Original GPS data (b) Adding Gaussian noise
(c) Discretizing data to a grid
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Data Source - NetSense Study
Provided 200 smart devices to incomingfreshmen at Notre Dame (Aug 2011)
200x Nexus S 4G200 anytime minsUnlimited data,
text User level agent
(1-3 min polling intervals)
Environment (WiFi, Cell)User proximity (Bluetooth)Phone state (Screen, Battery)Phone usage (data / app tonnage)
802.11n, 802.11g
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Notations
• MN = {MN1, MN2, MN3}
• AP = {AP1, AP2, AP3}
• NLit (WiFi Proximity Set), e.g., NL1
t = {AP1, AP2, AP3}
• NSit (B/T Proximity Set), e.g., NSi
t = {MN2, MN3}
• RL: WiFi radio range• RS
: B/T radio rangeThe vision of MN1 at
time t
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Approach
Problem DescriptionInput: wireless relationships (WiFi and B/T proximity)
constrained by RL and RS Output: trace solution for each mobile nodepreserving α of the given wireless relationships
Algorithm Components
Step 1: Access Point Deployment (2D)
Step 2: Mobility Trace Generation
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
AP DeploymentConnectivity Graph• Connected if detected by the same mobile device
• Infer AP-to-AP relative distances (shortest path)
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
AP Deployment
CMDS
Classic Multidimensional Scaling (Torgerson, 1952)
(Source: https://personality-project.org/r/mds.html)
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Trace Generation
AP deployment as the input
Location of a mobile device depends on locations of detected APs and MNs
Multiple solutions provide ambiguityp1, p2, p3 – candidate solutionsfor mobile node x
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Evaluation MetricsBluetooth proximity preservation w.r.t. RS o Precision: PNS
o Recall: RNS
o F_Score: FNS
N
i
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ti
NS TNNSretrieved
NSretrievedNSoriginalP
1 1
)/()|_|
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NSretrievedNSoriginalR
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NSNS
NSNSNS RP
RPF
2
WiFi proximity preservation w.r.t. RL (similar)
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Results
Bluetooth Proximity Preservation - Aggregate
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Results
WiFi Proximity Preservation - Aggregate
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Results F_Score Distribution: Bluetooth vs. WiFi proximity
preservation
WiFi Proximity:~80% nodes ≥
0.78 B/T Proximity:~95% nodes ≥
0.90
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Results Inter-contact Time Distribution: Original samples vs. Generated
traces
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Summary
A novel approach to preserve location privacy using zero knowledge of actual locations
Potential impact where traces are needed but not available
Metrics to evaluate the preservation of wireless relationships
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Open Problems
Introducing RSSI for better hint to relative distances3D space deployment
Security challenges (quantitatively measuring how much privacy gained)
UNIVERSITY of NOTRE DAMECOLLEGE of ENGINEERING
Questions?
Contact Information
Prof. Aaron Striegel : [email protected] Hu: [email protected]
NetSense Study: http://netsense.nd.edu/
