1. Enhancing Source-Location Privacy in
Sensor Network Routing
P. Kamat, Y. Zhang, W. Trappe and C. Ozturk
Proceedings of the 25th IEEE Int. Conference on Distributed Computing Systems
Rutgers University
Matthew Sanderson
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2. Presentation Outline
 Introduction to issue
 Panda vs Hunter
 Techniques for Stationary Sources
Routing Protocols
Performance Comparison
Improvement for privacy.
 (Briefly) Mobile Sources
 Related/Future Work
 Conclusion
 Questions
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3. The issue is privacy.
 “Guarantee that information is observable or decipherable
by only those who are intentionally meant to observe or
decipher it.”
 Two broad categories:
content-oriented
context-oriented
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4. Content-oriented Security/Privacy
 Security of the contents of
messages.
 Cryptographic methods.
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5. Contextual Privacy
 Deals with context in
which the sensor
application works.
 In this case: location
 Not as thoroughly
researched.
 What this paper covers.
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6. Source-location Privacy
 Privacy of the node sending the initial message.
 Two metrics:
safety period – how long until the node is
discovered
capture likelihood – how likely it will get discovered
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7. Accomplishing source-location privacy
 Look at popular routing techniques.
 Augment these techniques with a new approach.
 Energy consumption still important.
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8. Panda-Hunter Game Model Scenario
 Panda-Hunter Game:
A sensor network has been
deployed to monitor a panda
habitat.
Sensors send Panda_Here
messages
Messages are forwarded to a data
sink.
The hunter observes packets and
traces his way back to the panda.
 Privacy Goal: Increase the time
needed for an adversary to track
and capture the panda (safety Data Sink
period).
Sensor Node
Slide source: Wenyuan Xu
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9. Additional Game Setup Issues
 One panda – one source
 Additional Goal: deliver
messages to base station.
 Concern: energy usage.
Data Sink
Sensor Node
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10. The Hunter
 Non-malicious – does not
interfere with network
 Device-rich – has devices to
measure angle of arriving
message
 Resource-rich – move at any
rate and unlimited power
 Informed – knows how the
network works
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11. How the hunter gets each message.
 Two primary routing
techniques.
Flooding
Single-path
 New approach: Phantom
Routing.
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12. Routing Techniques - Flooding
 Flooding-based: source
sends the message to all
its neighbors, who in turn
do the same.
 If node has received it
already, the node discards
it.
 Performance drawbacks,
but easy implementation.
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13. Probabilistic Flooding
 Like flooding, but with a
probability.
 When a node receives a
message, it randomly
generates a number
uniformly distributed
between 0 and 1.
 If # < forwarding
probability, it sends,
otherwise, it doesn't.
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14. Single-Path Routing
 Instead of sending out to all
neighbors, single-path sends
out to one or a small subset
of neighbors.
 Usually require extra
hardware or a pre-
configuration phase.
Data Sink
Sensor Node
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15. How well do they work?
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16. Performance Comparison cont.
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17. Privacy of Routing Techniques
 Problems with single-path and flooding
Single-path reduces energy, but poor at protecting source-
location privacy.
Flooding isn't any better, because the shortest-path is still
contained within the flood.
Probabilistic flooding helps – higher safety period, but at the cost
of delivery ratio.
 There is room for improvement.
Maybe trick the hunter?
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18. Routing with Fake Sources
 Idea: inject fake messages
to throw off hunter.
 Multiple ways this can be
done.
Short-lived – similar to
probabilistic flooding.
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19. Persistent Fake Source
 Short-lived fake sources can only draw the hunter away
momentarily.
 A persistent fake source is more effective, but requires a
global overview of network.
 Source sends its hop count to sink – sink instigates a fake
source at a node with the same hop count in the opposite
direction.
 Works best when fake source sends at higher rate than
real source, but requires large energy budget.
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20. Problem with Fake Sources: Perceptive Hunter
 Recall the assumptions on our hunter – he's informed.
 Once he realizes the fake source, he knows which
direction to go for the real source.
 We need a new approach.
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21. Phantom Routing
 Idea: entice hunter to
phantom instead of
source.
 Has two phases:
Random walk phase
Flood/Single-path
phase
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22. Types of Random Walk
 Sector-based – requires
knowledge of landmark
nodes to send message
away from source.
 Hop-based – requires
knowledge of the hop
count from each node to
the base station.
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23. Phantom Routing Performance
 Can significantly improve
the safety period.
 Higher the hopcount,
higher the safety period.
 Also increases latency
(Random walk of 20: 30%
increase = 4x privacy).
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24. Possible Counter: Cautious Hunter
 Since the phantom routing may leave the hunter stranded,
after some time, the cautious hunter may go back.
 No benefit – no progress made by hunter.
 Better to be patient.
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25. Mobile Source
 Need to rethink entire
process again.
 Depends on panda's
movement pattern and
velocity.
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26. Panda Velocity
 More profound on single-path routing, as subsequent
route may have little overlap compared to flooding.
 Panda's speed with single-path is protection enough.
 Improves privacy of phantom routing.
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27. Hunter's Range
Not so surprising, if the
hunter's hearing range is
increased, the hunter is
more effective.
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28. Related/Future Material
 Entrapping Adversaries for Source Protection in Sensor Networks
Yi Ouyang, Zhengyi Le, Guanling Chen, James Ford, Fillia Makedon – Dartmouth College
 Preserving Source Location Privacy in Monitoring-based Wireless Sensor
Networks
Yong Xi, Loren Schwiebert, Weisong Shi – Wayne State University
 Location Privacy in Sensor Networks Against a Global Eavesdropper
Kiran Mehta, Donggang Liu, Matthew Wright – University of Texas at Arlington
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29. Conclusion
 The panda-hunter game is somewhat contrived.
Does a great job at visualizing concept.
 Concept is simple and effective.
 Source-location privacy for sensor networks seems to be
a minor issue.
I'm willing to admit I'm wrong here.
Come up with some examples.
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30. Questions?
?
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