A Two-Layer Key Establishment Scheme for Wireless Sensor Networks

1. A Two-Layer Key Establishment Scheme for Wireless Sensor Networks Yun Zhou, Student Member, IEEE, Yuguang Fang, Senior Member, IEEE IEEE TRANSACTIONS ON MOBILE COMPUTING 20083150 김진석

2. Contents • Introduction • Security and Key Management in WSNs • Overview of LAKE • Key Management in LAKE • Security Analysis and Performance Evaluation • Discussion and Conclusion

3. Introduction • WSN • Thousands of Resource-Limited Nodes Without Infrastructure • Unattended, Hostile Environment • Battlefield, Homeland Security Monitoring • Network Vulnerability to Malicious Attacks • Need of Security • Key Management • Base for Encryption, Authentication • How to Set Up Keys to Protect Connections between Nodes • Link Layer Key and Transport Layer Key

4. Introduction • LLK • One-hop Connection Between Neighbor • Shared LLK for Secure Link Layer Connection • Vulnerability to Node Compromise Attack • Secrets in Compromised Node is used to derive Secret Shared by Non-compromised Nodes • Compromised Can be Failure Point of Infrastructure • Large Memory Requirement • Certain Level of Security, Connectivity

5. Introduction • TLK • Multi-hop Connection Between Nodes • TLK for End-to-end Security • Memory Requirement Increases When Network is Large • Each Node Must Preload N-1 Keys • Relaxed Security Requirement • LLK between any pair of Neighboring Nodes Saving Memory • Based on LLK Infrastructure, Negotiate TLK over Multi-hop Path • On-demand TLK Negotiation • Vulnerability to Node Compromise Attack • Multi-hop Path can be Large

6. Introduction • Previous Work • Global Key -> Centralized Key Distribution • Distributed, LLK • Using Intersection of Shared Secret of Each Node • Key Predistribution (Random, Probabilistic Key Agreement) • Deterministic LLK Scheme • Location Based LLK Scheme • t-Degree Polynomial for Key Establishment

7. Overview of LAKE • two-LAyer Key Establishment • For Establishment of LLK and TLK • Nodes are in 2-dimensional Space (Logical) • Trivariate Polynomial is Predistributed • Used to Establish Keys • Neighbors are Pre-loaded with Correlated Secrets • Called Shares, Derived from Trivariate Polynomial • Proper Degree t assures Resilience to the Node Compromised Attack • 3 Phase : Share Predistribution, Direct Key Calculation, Indirect Key Negotiation

8. Overview of LAKE • Share Predistribution • Polynomial Coefficients are in Finite Prime Field • Symmetric • 2 Credential for each Nodes -> Univariate Polynomial • Node u (u1, u2), v (v1, v2) • One Common Credential -> Key Calculation

9. Overview of LAKE • Using Deployment Information • N1 non-overlapping Cells, N2 Nodes for each Cells • 2 Dimensional Space • Coordinate (n1, n2) is used for Credentials • c1 [N2+1,N1+N2] [1,N2] • Assumption • Gaussian Node Distribution in Cells • When Direct Key Calculation is unable, Indirect Key Negotiation can be done by Using underlying Routing protocol • Correctly Routes Key Negotiation Messages over Multi-hop Path

10. LAKE • Share is Pre-Distributed • Direct Key Calculation

11. LAKE • Indirect Key Negotiation • Using Level 2 Neighbor and Level 1 Neighbor • Intermediate Agent Node • Case : (v1, v2) (u1, u2) • Agent : (v1, u2), (u1, v2)

12. LAKE • LLK • Neighbors in Radio Radius • Direct Key Calculation Between Neighbors • Indirect Key Negotiation Between Nodes with Deployment Error • TLK • Dynamic Establishment of TLK (On Demand) • Similar to LLK Establishment • Direct Key Calculation for Level 2 Neighbors • Using Underlying Routing Protocol for Deployment Error • Secure Link • Two Nodes Already have Shared Key • No more than 1 Agent Node Needed.

13. Security Analysis and Performance Evaluation • Metrics • Resilience to the Node Compromise Attack • Node Compromise Attack is Unavoidable • Reducing Additional Key Exposure Probability • Local Secure Connectivity • Probability that two Neighboring Nodes Establish a Direct Key (Portion of Neighbors have Direct Keys) • Energy Consumption of Multihop Routing, Indirect Key Negotiation

14. Security Analysis and Performance Evaluation • Metrics • Memory Cost • How many memory units per node are needed • Polynomial Share Memory Requirement • Computational Overhead • Overhead in Calculation of Direct Keys • LAKE : Efficient Symmetric Key Technique

15. Security Analysis and Performance Evaluation • Memory Cost

16. Security Analysis and Performance Evaluation • Additional Key Exposure Probability

17. Security Analysis and Performance Evaluation • Local Connectivity

18. Security Analysis and Performance Evaluation • Computational Overhead

19. Conclusion • LAKE : t-Degree Polynomial Based Scheme • Sensor Nodes in 2-dimensional Space • Efficiently Establishes LLK and TLK • More Secure, Lesser Memory Use • Security to Node Compromise Attack • Compared with Conventional Schemes • Energy Efficient • Due to the Location-based Deployment • Neighbors can Calculate Key Directly, not Multi-hop

20. Discussion • Higher Dimensional Space • Higher Dimensional Multivariate Polynomial • Node Identification : k indices • t-Degree (k+1)-variate Polynomial • Same Approach for PIKE, HyperCube • Memory Cost is higher than LAKE • Given same amount of Memory Resource, LAKE achieves a Higher Security Level