PReFilter: An Efficient Privacy-preserving Relay
Filtering Scheme for Delay Tolerant Networks
Rongxing Lu, Xiaodong Lin, Tom Luan,
Xiaohui Liang, Xu Li, Le Chen, and Xuemin (Sherman) Shen
University of Waterloo & UOIT & INRIA Lille
Presenter: Rongxing Lu
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•
Introduction of Delay Tolerant Networks
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Security & Privacy Challenges in DTNs
•
Proposed PReFilter Scheme
•
Security Analysis
•
Performance Evaluation
•
Conclusions
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Infrastructure

Non-infrastructure
•
High density

Low density
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Performance : Highly depend on mobility
•
Delay Tolerant Network (DTN)

High transmission delay

Frequent link disruption

Non-exist end-to-end connections
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Inter-planetary communication Vehicular Ad-hoc Network
Networking in sparse rural area Underwater Sensor Network
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R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

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DTN Routing
 increase the delivery ratio
 reduce the average delay
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Single copy

Multi-copy
S
D
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Balance Performance & Resource Consumption

Probabilistic routing

Spray and wait
 Relaycast
[1] A. Lindgren, A. Doria, and O. Schelen, “Probabilistic routing in intermittently connected networks,” Mobile Computing and
Communications Review, vol. 7, no. 3, pp. 19–20, 2003.
[2] T. Spyropoulos, K. Psounis, and C. S. Raghavendra, “Spray and wait: an efficient routing scheme for intermittently connected mobile networks,” in Proc. of WDTN ’05, 2005, pp. 252–259.
[3] U. Lee, S. Y. Oh, K.-W. Lee, and M. Gerla, “Relaycast: Scalable multicast routing in delay tolerant networks,” in Proc. of
ICNP’08, 2008.
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Without solving security issues
 well-designed DTN routing not practical
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Selfish issues
 incentive mechanism
 avoid black/grey hole
D
Selfish
Incentive
S
Selfish
Selfish
[1] S. Upendra, H. H. Song, L. Qiu, and Y. Zhang, “Incentive-aware routing in dtns,” in Proc. of ICNP’08, 2008, pp. 238–247.
[2] R. Lu, X. Lin, H. Zhu, X. Shen, and B. R. Preiss, “Pi: a practical incentive protocol for delay tolerant networks,” IEEE
Transactions on Wireless Communications, vol. 9, no. 4, pp. 1483–1493, 2010.
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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(2)
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Traffic storm problem
 caused by the malicious nodes
 false data  waste scarce DTN resources
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Countermeasure
 fundamental packet authentication
 access control
 detect false data by relay nodes
 drop false data early
 save scarce DTN resources
S
D
[1] N. Asokan, K. Kostiainen, P. G. J. Ott, and C. Luo, “Towards securing disruption-tolerant networking,” Nokia Research, Tech.
Rep. NRC-TR-2007-007.
[2] H. Zhu, X. Lin, R. Lu, X. Shen, D. Xing, and Z. Cao, “An opportunistic batch bundle authentication scheme for energy constrained DTNs,” in Proc. IEEE INFOCOM’10, 2010, pp. 605–613.
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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(3)
• Encrypted “junk” packet --- New Challenge
 encrypted, sent by the legitimate nodes
 “junk”  of no interest to the destination
 decrypted, discarded by the destination
D
•
But, before being discarded
 TTL expire
 or encounter with destination
 also waste scarce DTN resources
S
•
No countermeasure, ▼
 encrypted
 sent by legitimate nodes
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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From traditional Email System

DTN
Filtering
Keyword
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Differences

Transmission: Infrastructure

DTN nodes

Filtering: centralized
 decentralized (effectively filter)

Privacy: protected
 easily violated
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Our Contribution

PReFilter: Privacy-preserving relay filtering for DTN
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Each node sets its filtering keyword list
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Distribute encrypted keyword list to its friends
 friends can use the encrypted keyword list for filtering
 but cannot read the keywords in plaintext
FP i
1
N
1
Rule 1
Rule 2
- - -
N i
FP i
5
Social Connection
FP i
2
N
5
N
7
N
2
N
2
N
1 FP i
4
N
8
N
6
N
3
3
FP i
N
N
3 •
Packet format
4
Sparse DTN
Destination Keyword Payload TTL Authenticator
N
4
N
5
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R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

PReFilter Mechanism
D
S
Junk packet
S Source D Destination
Intermediate node w/o packet dropping
Destination’s friend
Intermediate node with packet dropping
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Achieve
 privacy-preserving policy distribution
 privacy-preserving filtering
 integrity, confidentiality
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Performance Evaluation
1000 m x 1000 m
Simulation Area Random waypoint model
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Performance Evaluation
Delivery ratio in forwarding ordinary beneficial packets with different n , v and tr
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Performance Evaluation
Average delay and network storage cost in forwarding ordinary beneficial packets with different n , v and tr
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Performance Evaluation
Average network storage cost in forwarding a “junk” packet under
PReFilter with different n , v and tr
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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Performance Evaluation
Average replicas distribution of a “junk” packet under with different n , v and tr
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks
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In this talk, we have discussed a Privacypreserving relay filtering (PReFilter) scheme for
DTNs

Privacy-preserving filtering policy distribution
 Relay node to filter “junk” packets as early as possible

Avoid the significant waste of scarce DTN resources
•
In our future work,

Heterogeneous mobility of DTN nodes
 Distribute the filtering policy at high social friend nodes
Thank you!
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R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks