1. University of Waterloo & UOIT & INRIA Lille Presenter: Rongxing Lu
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

2. Outline Introduction of Delay Tolerant Networks
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

3. Introduction Infrastructure  Non-infrastructure
High density  Low density
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

4. Applications of DTN Inter-planetary communication
Vehicular Ad-hoc Network
Networking in sparse rural area
Underwater Sensor Network
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

5. DTN Routing DTN Routing Single copy  Multi-copy
increase the delivery ratio
reduce the average delay
Single copy  Multi-copy
Balance Performance & Resource Consumption
Probabilistic routing
Spray and wait
Relaycast D S
[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

6. Security Challenges Without solving security issues Selfish issues
well-designed DTN routing not practical
Selfish issues
incentive mechanism
avoid black/grey hole D S
Selfish
Selfish
Incentive
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

7. Security Challenges (2)
Traffic storm problem
caused by the malicious nodes
false data  waste scarce DTN resources
Countermeasure
fundamental packet authentication
access control
detect false data by relay nodes
drop false data early
save scarce DTN resources D S
[1] N. Asokan, K. Kostiainen, P. G. J. Ott, and C. Luo, “Towards securing disruption-tolerant networking,” Nokia Research, Tech. Rep. NRC-TR
[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

8. Security Challenges (3)
Encrypted “junk” packet --- New Challenge
encrypted, sent by the legitimate nodes
“junk” of no interest to the destination
decrypted, discarded by the destination
But, before being discarded
TTL expire
or encounter with destination
also waste scarce DTN resources
No countermeasure, ▼
encrypted
sent by legitimate nodes D S
Big Challenge
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

9. Our Contribution From traditional Email System  DTN Differences
Transmission: Infrastructure  DTN nodes
Filtering: centralized  decentralized (effectively filter)
Privacy: protected  easily violated
Our Contribution
PReFilter: Privacy-preserving relay filtering for DTN
Filtering Keyword
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

10. Our PReFilter Scheme Each node sets its filtering keyword list
Distribute encrypted keyword list to its friends
friends can use the encrypted keyword list for filtering
but cannot read the keywords in plaintext
Packet format
Rule 1
Rule 2
- - -
Destination
Keyword
Payload
TTL
Authenticator
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

11. PReFilter Mechanism D S Junk packet S Source D Destination
Destination’s friend
Intermediate node w/o packet dropping
Intermediate node with packet dropping
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

12. Security Analysis 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

13. Performance Evaluation
Simulation Area
Random waypoint model
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks

14. 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

15. 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

16. 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

17. 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

18. Conclusion
In this talk, we have discussed a Privacy-preserving 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!
R. Lu et al., PReFilter: An Efficient Privacy-preserving Relay Filtering Scheme for Delay Tolerant Networks