Secrecy Capacity Scaling of Large-Scale Cognitive Networks

1. Secrecy Capacity Scaling of Large-Scale Cognitive Networks Yitao Chen1, Jinbei Zhang1, Xinbing Wang1, Xiaohua Tian1, WeijieWu1, Fan Fu2, Chee Wei Tan3 1 Dept. of Electronic Engineering, Shanghai Jiao Tong University 2 Dept. of Computer Science and Engineering, Shanghai Jiao Tong University 3 Dept. of Computer Science, City University of Hong Kong

2. Outline • Introduction • Network Model and Definition • Independent Eavesdroppers • Colluding Eavesdroppers • Conclusion

3. Motivations • Security is a major concern in wireless networks • Virtual Property • Mobile Payment • Military Communication • Privacy

4. Motivations • Physical Layer Security • Assume eavesdroppers have infinite computation power • Require the intended receiver should have a stronger channel than eavesdroppers • Provable security capacity • Cryptographic methods • Key distribution • Rapid growth of computation power • Improvement on decoding technology

5. Related works • Secrecy capacity in large-scale networks • Guard zone [9] • Artificial noise + Fading gain (CSI needed) [8] • Using artificial noise generated by receivers to suppress eavesdroppers’ channel quality [11] Cited from [8] [9] O. Koyluoglu, E. Koksal, E. Gammel, “On Secrecy Capacity Scaling in Wireless Networks”, IEEE Trans. Inform. Theory, May 2012. [8] S. Vasudevan, D. Goeckel and D. Towsley, “Security-capacity Trade-off in Large Wireless Networks using Keyless Secrecy,” in Proc. ACM MobiHoc, Chicago, Illinois, USA, Sept. 2010. [11] J. Zhang, L. Fu, X. Wang, “Asymptotic analysis on secrecy capacity in large-scale wireless networks,” in IEEE/ACM Trans. Netw., Feb. 2014.

6. Motivations • Limited spectrum resources and CR networks • Key questions: • What is the impact of security in cognitive networks? • What is the performance we can achieve?

7. Outline • Introduction • Network Model and Definition • Independent Eavesdroppers • Colluding Eavesdroppers • Conclusion

8. Network Model and Definition – I/III • Network Area: a square • Legitimate Nodes • primary users , secondary users • I.I.D • Self-interference cancelation [17] adopted • CSI unknown • Eavesdroppers • eavesdroppers • Location positions unknown • CSI unknown Cited from [17] [17] J. I. Choiy, M. Jainy, K. Srinivasany, P. Levis and S. Katti, “Achieving Single Channel, Full Duplex Wireless Communication”, in ACM Mobicom’10, Chicago, USA, Sept. 2010.

9. Network Model and Definition – II/III • Random permutation traffic, no cross network traffic • Communication Model • Physical Model: Primary user i transmits to primary user j • Define the physical model for secondary users and eavesdroppers similarly. Interference from other primary TXs Interference from other primary RXs Interference from secondary TXs Interference from secondary TXs

10. Network Model and Definition – III/III • Definition of Per Hop SecrecyThroughput: • Independent eavesdropper • Colluding eavesdroppers • Definition of Asymptotic Capacity • Similarly, we can define the asymptotic per-node capacity for the secondary network , if

11. Outline • Introduction • Network Model and Definition • Independent Eavesdroppers • Colluding Eavesdroppers • Conclusion

12. Independent Eavesdroppers • Physical Feasibility of Security • Primary Networks • and • Secondary Networks • and • Operation Rules: • Primary users disregard secondary users; • Secondary users should affect primary users little. No eavesdropper can decode the message Successful transmission

13. Independent Eavesdroppers • Intuitive • Primary Networks • Concurrent Transmission Range • Secrecy Capacity • Secondary Networks • Unknown • ? Good or bad for primary nodes • ? Good or badfor eavesdroppers • Depend on SUs’ locations

14. Independent Eavesdroppers • Primary T-R pair (node i to node j) • For other primary transmitter k and receiver l • For other secondary transmitter k and receiver l

15. Independent Eavesdroppers • Scheduling scheme • Cell Partition Round-Robin Scheduling: • Tessellate the network into cells. • Different cells take turn to transmit. • Secondary users can transmit in non-occupied cells with the guarantee of affecting primary transmissions little. Figure: Simple 9-TDMA

16. Independent Eavesdroppers No order cost comparing to the scenario without security concern! • Routing scheme • Highway System • Draining Phase • Highway Phase • Delivery Phase Bottleneck: Highway Phase (nodes need to relay packets for others) • Distance of primary T-R pairs is 1. • Secrecy Capacity is for primary network. • Secrecy Capacity is for secondary network.

17. Outline • Introduction • Network Model and Definition • Independent Eavesdroppers • Colluding Eavesdroppers • Difference with previous case • Conclusion

18. Colluding Eavesdroppers • SINR of Colluding Eavesdroppers • maximum ratio combining of SINR Bound the SINR of eavesdroppers: • Disjoint rings with same size. • Eavesdroppers in the same ring has a similar SINR. • Artificial noise + Path loss gain + Cooperation

19. Colluding Eavesdroppers when choosing and is a constant. • Choice of Concurrent Transmission Range k • k , artificial noise , throughput • k , SINR of eavesdroppers , security

20. Colluding Eavesdroppers • Result comparison Cooperation in cognitive networks helps to increase secrecy capacity, compared to stand-alone networks [11]. [11] J. Zhang, L. Fu, X. Wang, “Asymptotic analysis on secrecy capacity in large-scale wireless networks,” to appear in IEEE/ACM Trans. Netw., 2013.

21. Outline • Introduction • Network Model and Definition • Independent Eavesdroppers’ Case • Colluding Eavesdroppers’ Case • Conclusion

22. Conclusion • In this paper, we study physical layer security in cognitive networks. • Our scheme adopting self-interference cancellation is very efficient. • Cooperation between secondary network and primary network in CR networks can help to strengthen physical layer security.

23. Thank you !