Securing Wireless Sensor Networks

1. Securing Wireless Sensor Networks Wenliang (Kevin) Du Department of Electrical Engineering and Computer Science Syracuse University Excerpted from http://www.cis.syr.edu/~wedu/Research/slides/Purdue04.ppt

2. Overview • Overview of Wireless Sensor Networks (WSN). • Security in wireless sensor networks. • Why is it different? • Our work on key pre-distribution in WSN • Deployment-based scheme (INFOCOM’04) • Pair-wise Scheme (ACM CCS’03) • Summary.

3. Wireless Sensors Berkeley Motes

4. Mica Motes • Mica Mote: • Processor: 4Mhz • Memory: 128KB Flash and 4KB RAM • Radio: 916Mhz and 40Kbits/second. • Transmission range: 100 Feet • TinyOS operating System: small, open source and energy efficient.

5. Spec Motes

6. Deploy Wireless Sensor Networks (WSN) Sensors

7. Applications of WSN • Battle ground surveillance • Enemy movement (tanks, soldiers, etc) • Environmental monitoring • Habitat monitoring • Forrest fire monitoring • Hospital tracking systems • Tracking patients, doctors, drug administrators.

8. Securing WSN • Motivation: why security? • Why not use existing security mechanisms? • WSN features that affect security. • Our work: • Two key management schemes.

9. Why Security? • Protecting confidentiality, integrity, and availability of the communications and computations • Sensor networks are vulnerable to security attacks due to the broadcast nature of transmission • Sensor nodes can be physically captured or destroyed

10. Why Security is Different? • Sensor Node Constraints • Battery, • CPU power, • Memory. • Networking Constraints and Features • Wireless, • Ad hoc, • Unattended.

11. Sensor Node Constraints • Battery Power Constraints • Computational Energy Consumption • Crypto algorithms • Public key vs. Symmetric key • Communications Energy Consumption • Exchange of keys, certificates, etc. • Per-message additions (padding, signatures, authentication tags)

12. Constraints (Cont.)Public Key Encryption • Slow • 1000 times slower than symmetric encryption • Hardware is complicated • Energy consumption is high

13. Memory Constraints • Program Storage and Working Memory • Embedded OS, security functions (Flash) • Working memory (RAM) • Mica Motes: • 128KB Flash and 4KB RAM

14. Objectives of Our Research • Long-term Goals • Study how WSN’s constraints/features affect the design of security mechanisms. • Develop security mechanisms for WSN. • Current Projects • Key Management Problems • Data Fusion Assurance

15. Key Management Problem

16. Deploy Key Management Problem Sensors

17. Deploy Key Management Problem Sensors Secure Channels

18. Approaches • Trusted-Server Schemes • Finding trusted servers is difficult. • Public-Key Schemes • Expensive and infeasible for sensors. • Key Pre-distribution Schemes

19. Key Pre-distribution • Loading Keys into sensor nodes prior to deployment • Two nodes find a common key between them after deployment • Challenges • Memory/Energy efficiency • Security: nodes can be compromised • Scalability: new nodes might be added later

20. Naïve Solutions • Master-Key Approach • Memory efficient, but low security. • Needs Tamper-Resistant Hardware. • Pair-wise Key Approach • N-1 keys for each node (e.g. N=10,000). • Security is perfect. • Need a lot of memory and cannot add new nodes.

21. Eschenauer-Gligor Scheme Key Pool S Each node randomly selects m keys A B C D E • When |S| = 10,000, m=75 • Pr (two nodes have a common key) =0.50

22. Establishing Secure Channels B A D C E

23. Exercise 7 • Write a program to calculate the probability: • Input: • G=(V,E) • Pr (two nodes have a common key) = • Output: • Let E’E denote the subset of secure channels, calculate the probability that G=(V,E’) is a connected graph. • Due: June 4th

24. Example 1 • =1/2

26. Example 2 • =2/3

27. 3 1 2 2 3 3 1 |V|=3 Undirected edges (1,2) (2,3) (3,1) Note: the given graph may not be complete. Input Format