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

3.  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 Introduction

4.  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 Introduction

5.  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 Introduction

6.  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 Introduction

7.  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 Overview of LAKE

8.  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 Overview of LAKE

9.  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 Overview of LAKE

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

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

12.  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. LAKE

13.  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 Security Analysis and Performance Evaluation

14.  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 Security Analysis and Performance Evaluation

15.  Memory Cost Security Analysis and Performance Evaluation

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

17.  Local Connectivity Security Analysis and Performance Evaluation

18.  Computational Overhead Security Analysis and Performance Evaluation

19.  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 Conclusion

20.  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 Discussion