evaluating lbs privacy in dynamic context
DESCRIPTION
Evaluating LBS Privacy In DYNAMIC CONTEXT. Implement report (12/05/2011). Outline. Architecture Implement Merge module Algorithm module Reciprocity module Experiment Conclusion. Outline. Architecture Implement Merge module Algorithm module Reciprocity module Experiment - PowerPoint PPT PresentationTRANSCRIPT
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EVALUATING LBS PRIVACY IN DYNAMIC CONTEXTImplement report (12/05/2011)
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Implemented algorithms Nearest-neighbor ASR (nnASR)
R-Tree Index Different results when run many times with
same input Interval Cloaking
Quad-Tree index Same input – same result
Grid Sorted List Same input – same result
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Checking reciprocity module Input: issuer id + MBR Output: number of users which have same
MBR – real k Algorithm:
Set k_anonymity = 0 Run anonymizing algorithm to get AS For each id ui in AS, run algorithm to get ASi
If AS = ASi then k_anonymity = k_anonymity + 1 If k_anonymity >= k, return true Else return false
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Problem with reciprocity property
An assumption about anonymizing algorithm: In snapshot, same input same result
Problem Algorithm: same input different results
Example: nnASR
II
1st time 2nd time
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nnASR: an attack proposed Assumption
K is known Idea
Find the chosen users Its k-nn must be in or be the original MBR
Forecast the candidate issuer For each user in original MBR (exclude chosen
users) Check whether its k-nn include one of chosen users
& expand MBR is equal to original MBR True candidate
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Illustration k = 4
Candidate
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Illustration k = 4
Candidate
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Refine algorithm Just refine value k of request Brute-force:
Increase k until request satisfies reciprocity property
Suitable for algorithms which: Same input same result
Problem: nnASR
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Outline Architecture Implement
Merge module Algorithm module Reciprocity module
Experiment Conclusion
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Experiment Implement the algorithms in Java System configuration:
OS: Window 7 Processor: AMD Phenom II X4 B40 3.0Ghz RAM: 2GB
Data: users’ locations in Sanfrancisco with 17000 users
Run 500 tests and take the average to get output values
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Experiment
4 6 8 10 12 14 16 18 200.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
1.800
2.000
Average computation time
GridnnASRInterval
k
Tim
e (m
s)
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Experiment
4 6 8 10 12 14 16 18 200.000
20,000.000
40,000.000
60,000.000
80,000.000
100,000.000
120,000.000
140,000.000
160,000.000
GridnnASRInterval
k
Perim
eter
(m
)
Average size of the generalized region
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Experiment
1 2 3 4 5 6 7 8 90
200
400
600
800
1000
1200
Average computation time for checking & refin-ing
GridInterval
k
Tim
e (m
s)
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Conclusion nnASR algorithm: how to improve
privacy of user? The performance of reciprocity module