Source: Lecture Notes in Computer Science, Vol. 6018, pp. 291-304, 2010.

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

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

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

5. Cluster-Based Deployment Model • Notation (2) • r: number of nodes in a cluster • p: probability • Bu: the broadcasting message of node u • kuv: pairwise key shared by node u and v • Nu: random value generated by node u • k_ID_uvw1: common key’s ID of node u, v • Ekuc{M}: cipher text of message M encrypted by key kuc

6. Cluster-Based Deployment Model Cluster Cluster Key Pool P N1 m N2 m m N C-Head Sub-Key Pool M m Cluster Cluster N m m m m N m The Network Topology of the Cluster-Based Deployment Model

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

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

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

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

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

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

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

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:

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

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

17. Performance Analysis • Security Analysis

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

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