1. A scalable key pre-distribution mechanism for large-scale wireless sensor networks Author: A. N. Shen, S. Guo, H. Y. Chien and M. Y. Guo Source: Concurrency and Computation-Practice & Experience, vol. 21, no. 10, pp.1373-1387, 2009. (Impact Factor = 1.004) Presenter: Yung-Chih Lu ( 呂勇志 ) Date: 2010/09/17 1

2. Outline Introduction Improved Key Distribution Mechanism Proposed Scheme Performance Evaluation Security Analysis Conclusion Comment 2

3. Introduction (1/4) Large-scale WSN WSN: Wireless Sensor Network 3

4. Introduction (2/4) Goal ◦ Key agreement ◦ Against attack  node capture attack ◦ Saving resource  communication cost  computation cost  storage overhead 4

5. Blundo Polynomial-based protocol  Setup server randomly generates a symmetric bivariate t-degree polynomial Example: f(x,y) = 4x 2 y 2 + x 3 y 1 + x 1 y 3 + 5 It’s a symmetric bivariate 3-degree polynomial Introduction (3/4) C. Blundo, A.D. Santis, A. Herzberg, S. Kutten, U. Vaccaro, M. Yung. "Perfectly-secure Key Distribution for Dynamic Conferences." Lecture Notes in Computer Science,471–486, 1993. [ ] 5 ０ ０ ０ ０ ０ ０ １ ０ ０ ４ ０ ０ １ ０ ０ 5

6. Blundo Polynomial-based protocol Introduction (4/4) L-sensor: Low-end sensor s: Step :L v -sensor 5141 y 0 y 1 y 2 y 3 :Cluster head step1: computes 1: Cluster Head ID 2: Lv-sensor ID f(1,y) = 4y 2 + y 1 + y 3 + 5 f(2,y) = 16y 2 + 8y 1 + 2y 3 + 5 step2: The Setup server loads the sensor node with coefficients step3: Each sensor node broadcasts its own ID step4: Receiver use ID to compute a shared secret key K uv = f(u,v) = f(v,u) = K vu K 12 = f(1,2) = 31 = f(2,1) = K 21 58 16 2 y 0 y 1 y 2 y 3 6 s3 s4

7. Improved Key Distribution Mechanism (1/3) Key pre-distribution phase ◦ Cluster head  ◦ Sensor node   CH a id and CH b id Y. Cheng and D. P. Agrawal, "improved key distribution mechanism for large-scale hierarchical wireless sensor networks." Journal of Ad Hoc Networks, vol.5, no.1, pp.35–48, 2007. BS: base station f(x,y): t-degree bivariate symmetric polynomial CH i : Cluster head i CH: Set of cluster heads in a network S i : Sensor node i K A-B : Symmetric key between A and B 7

8. Improved Key Distribution Mechanism (2/3) Inter-cluster pairwise key establishment ◦ step1: CH a and CH b exchange their node id each other ◦ step2: 8 f(x,y): t-degree bivariate symmetric polynomial CH i : Cluster head i CH: Set of cluster heads in a network K A-B : Symmetric key between A and B s: step 8 :CH a :CH b s1 s2

9. Improved Key Distribution Mechanism (3/3) Intra-cluster pairwise key establishment step1: S i sends its id, CH a id and CH b id to its CH j. step2: CH j sends S i to CH a and CH b. step3: CH u sends back to CH j., t=1,2 u=a,b step4: CH j decrypts to get k t. step5: CH a : :CH j :CH b :S i CH j : Cluster head j S i : Sensor node I s: step 9 s1 s2 s3 s4,s5

10. Proposed Scheme (1/3) Key pre-assignment phase ◦ Cluster head  ◦ Sensor node  BS: base station K A,B : Symmetric key between A and B CH i : Cluster head i with Id SN i : Sensor node i with Id f(x,y): t-degree bivariate symmetric polynomial 10

11. Proposed Scheme (2/3) Inter-cluster pair-wise key establishment phase Step1: Step3: Step4: Step2: 11 :CH a :CH b s1,s2 s3,s4

12. Proposed Scheme (3/3) Intra-cluster pair-wise key establishment phase Step1: Step3: Step4: Step2: 12

13. Performance Evaluation (1/2) Storage cost and Computational cost 13 n: the number of low-end sensor node t: the degree of polynomial m: the number of cluster head SKPD: our scheme

14. Performance Evaluation (2/2) Communication cost 14 LEKM: Low-Energy Key Management SKPD: our scheme IKDM: Improved Key Distribution Mechanism

15. Security Analysis (1/2) Initialization of the network 15 LEKM: Low-Energy Key Management SKPD: our scheme IKDM: Improved Key Distribution Mechanism

16. Security Analysis (2/2) After deployment of the network 16 LEKM: Low-Energy Key Management SKPD: our scheme IKDM: Improved Key Distribution Mechanism

17. Conclusion Best network resilience against node capture attack Communication overhead scheme is zero lowest energy consumption Reduces the key storage overhead Suitable for large-scale WSNs 17

18. Comment elasticity of demand is a lack of this scheme. other attacks 18