1 Securing Wireless Sensor Networks Wenliang (Kevin) Du Department of Electrical Engineering and Computer Science Syracuse University Excerpted from

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 Wireless Sensor Networks (WSN) Deploy 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 Slow –1000 times slower than symmetric encryption Hardware is complicated Energy consumption is high Constraints (Cont.) Public Key Encryption ProcessorEnergy Consumption (mJ/Kb) RSA/E/VRSA/D/SAES MIPS R MC

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 Key Management Problem Deploy Sensors

17 Key Management Problem Secure Channels Deploy Sensors

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

19 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 Key Pre-distribution

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 Each node randomly selects m keys A BE Key Pool S DC When |S| = 10,000, m=75 Pr (two nodes have a common key) = 0.50

22 Establishing Secure Channels A C B D 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 4 th

24 Example 1  =1/2

25

26  =2/3 Example 2

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