1. Efficient Pairwise Key Establishment Scheme Based on Random Pre-Distribution Keys in Wireless Sensor Networks Source: Lecture Notes in Computer Science, Vol. 6018, pp. 291-304, 2010. Authors: Hao Wang, Jian Yang, Ping Wang, and Pu Tu Presenter: Hsing-Lei Wang Date: 2011/02/18

2. Outline Introduction Cluster-Based Deployment Model Efficient Pairwise Key Establishment and Management Performance Analysis Conclusion Comments 2

3. Introduction Main contributions: ▫Propose the new cluster-based model of the network topology ▫Present the pairwise key establishment scheme Advantages: ▫Better connectivity and security ▫Lower communication and computational overhead ▫More scalable and flexible network size 3

4. Cluster-Based Deployment Model Notation (1) ▫P: key pool ▫|P|: size of key pool ▫M: sub key pool ▫|M|: size of sub key pool ▫m: number of keys in each node’s key ring ▫n: network size ▫t: number of clusters ▫Ni: Node identifier 4

5. Cluster-Based Deployment Model Notation (2) ▫r: number of nodes in a cluster ▫p: probability ▫B u : the broadcasting message of node u ▫k uv : pairwise key shared by node u and v ▫N u : random value generated by node u ▫k_ID_uvw 1 : common key’s ID of node u, v ▫E k uc {M}: cipher text of message M encrypted by key k uc 5

6. Cluster-Based Deployment Model 6 The Network Topology of the Cluster-Based Deployment Model Key Pool P Sub-Key Pool M Cluster N1N1 N2N2 N N N C-Head m m m m m m m m m

7. Efficient Pairwise Key Establishment and Management Establishment of the Pairwise Keys Directly Establishment of the Pairwise Keys via Intermediate Nodes 7

8. Establishment of the Pairwise keys Directly (1/3) Node u find the common keys by broadcasting a message to its neighbor nodes 8

9. Establishment of the Pairwise keys Directly (2/3) Assume a node v received the message, it will compare all the node u keys’ ID with its own keys’ ID, then reply their common keys’ ID to the node u 9

10. Establishment of the Pairwise keys Directly (3/3) The common keys will be stored in a form as Table 1 They take the first common key as their pairwise key 10

11. Establishment of the Pairwise Keys via Intermediate Nodes (1/4) 11

12. If node v found that there is no common key with node u, it then returns a message to u 12 Establishment of the Pairwise Keys via Intermediate Nodes (2/4)

13. Node u receives the message, stores N v, and selects node a, c to forward the key’s materials to node v 13 Establishment of the Pairwise Keys via Intermediate Nodes (3/4)

14. Establishment of the Pairwise Keys via Intermediate Nodes (4/4) If node a, c have the pairwise keys with node v, they transmit the messages to node v. The node u and node v can calculate a new pairwise key: 14

15. Performance Analysis Network Connectivity (1/2) 15 |P|=10,000

16. Performance Analysis Network Connectivity (2/2) 16

17. Performance Analysis Security Analysis 17

18. Conclusion Compared to the EG Scheme and the Chan et al. Scheme, this scheme has some properties: ▫Better network connectivity and resiliency ▫Much more scalable and flexible for network size ▫Lower computational and communication overhead 18

19. Comments The cluster head management mechanisms should be described The analysis of the computational and communication overhead should show the comparison of the overhead by numbers The authors have not compare their scheme to the EG scheme and Chan et al. scheme in network connectivity 19