1. A Routing-Driven Elliptic Curve Cryptography Based Key Management Scheme for Heterogeneous Sensor Networks Author: Xiaojiang Du, Guizani M., Yang Xiao and Hsiao-Hwa Chen Source: Wireless Communications, IEEE, vol.8, no.3, pp.1223-1229, 2009 Presenter: Yung-Chih Lu Date: 2010/07/13

2. Outline Introduction Related Work  L. Eschenauer and V. Gligor. “A Key-Management Scheme for Distributed Sensor Networks.” In Proc. 9th ACM Conference on Computerand Communication Security, pp.41-47, Nov. 2002. Proposed Scheme Performance Evaluaton Security Analysis Conclusion & Comment

3. Introduction(1/6) MANET (Mobile Ad Hoc Network) WSN (Wireless Sensor Network)

4. Introduction(2/6) SimilaritiesMANETWSN Multi-hop routingYes Auto-configurable wireless networksYes Self-healingYes Mobility of nodesYes unlicensed spectrumYes DifferencesMANETWSN Limited computationNoYes Global identificationYesNo Prone failuresNoYes Base stationNoYes Densely deployed in environmentNoYes The Topology changes frequentlyNoYes

5. Introduction(3/6) Sensor node constraints  Battery power Computational energy consumption Communication energy consumption  Transmission range  Memory space  Tamper protection Evaluation/Comparison metrics  Resilience against node capture  Addition  Revocation  Supported network size  suite all needs

6. E-G Scheme(1/3) Key pre-distribution phase Key pool (2 17 -2 20 keys) Key pool (2 17 -2 20 keys) Key ring (m keys) Key ring (m keys) Key ring (m keys) ……  two neighboring nodes have at least one the same key in their key rings

7. E-G Scheme(2/3) Shared-key discovery Key ring (m keys) Key ring (m keys) Key ring (m keys) wireless sennor node discovers its neighbors to find the common shared-key in their key ring the connected graph of secure link is formed

8. E-G Scheme(3/3) Path-key establishment Key ring (m keys) Key ring (m keys) Source sensor node Target sensor node Path key

9. Proposed Scheme(1/4) Centralized Key Establishment (1)Send E K R L [ Key-request message ] (L-sensor ID and location) (2) D K U L [E K R L [ Key-request message ]] = Key-request message (3)run Centralized MST algorithm to determine the tree structure (4) disseminates the parent-child relationships to all L-sensors (5)Send E K U L [K u,v ] (6) D K R L [E K U L [Ku,v]] = Ku,v

10. Proposed Scheme(2/4) Centralized Key Establishment L-sensor: K U H 、 K U L and K R L H-sensor: K U H 、 K R H all L U L and special key K H K H is used by a symmetric encryption algorithm KHKH new KHKH

11. Proposed Scheme(3/4) Distributed Key Establishment (1)Send E K R L [ Key-request message ] (L-sensor ID and location) (2) D K U L [E K R L [ Key-request message ]] = Key-request message (3)run Centralized MST algorithm to determine the tree structure (4) disseminates the parent-child relationships to all L-sensors (5)Send public key certificate E K R H [ K U L ] (6)Proves the authenticity of a public key

12. Proposed Scheme(4/4) Distributed Key Establishment uv (1)Send K U u (2)Send K U v (4)K R u K U v (3)K R v K U u K u,v = K R u K U v = K R v K U u

13. Performance Evaluation(1/2) Storage Saving Cluster Head Other Sensors E-G SchememMmN Proposed Scheme- Centralized (N+3)M2N Proposed Scheme- Distributed 3M2N E-G:64-bit key ECC:160-bit key E-G Scheme : ECC-Centralized : ECC-Distributed = 29.7 : 10.2 : 1

14. Performance Evaluation(2/2) n :the number of communication neighbors

15. Security Analysis(1/2) Proposed Scheme  each sensor is preloaded with one unique private key.  Each pair of communicating sensor has a different shared key. E-G Scheme  Compromising probability C(m) = Σ[(1-(1-m/P) c ) j p(j)] / Σp(j) p(j) = ( P j )( P-j 2(m-j) )( 2(m-j) m-j ) / ( p m ) 2 p(1) = m!(P-m)!(P-m)!/P!m!(P-2m)! m j=1 m

16. Security Analysis(2/2) E-G SchemeProposed Scheme Resilience against node capture C(m)0 AdditionEstablishes a key ring Establishes shared key RevocationRevokes the key ring Revokes the shared key Supported network size Smalllarge Suite all needsNo Evaluation/Comparison metrics

17. Conclusion & Comment A sensor only communicates with a small portion of its neighbors Proposed scheme significantly reduces sensor storage Proposed scheme significantly reduces Communication overhead Energy consumption while achieving better performance How to manages special key K H