A Security Protocol for Sensor Networks Khadija Stewart, Themistoklis Haniotakis and Spyros Tragoudas Dept. of Electrical and Computer Engineering Southern Illinois University

2 Outline Abstract Previous work Proposed method Uncorrelating the bits Encryption scheme Reverse uncorrelation and decryption scheme Hardware overhead Experimental results Conclusions

3 Abstract Sensor networks are extensively used in military and rescue operations Need for secure communications Memory, computational and energy resource constraints Security protocol must use minimal resources Available security schemes are either inefficient or expensive

4 Previous Work Key based schemes Frankel et al 1989 Eshenaur et al 2002 Chan et al 2003 Liu et al 2003 Du et al 2005

5 Previous Work Keyless methods target flexibility Rabin 1989 Papadimitratos et al 2003

6 Proposed Method: Outline Message split into 2n sub-messages Sub-messages uncorrelated using an LFSR Sub-messages encrypted Encrypted sub-messages are routed through transmission disjoint routes At the destination, sub-messages are decrypted and uncorrelation is reversed

Globecom 057 Proposed Method: Splitting of the message a0a0 a1a1 a2a2 a3a3 a4a4 a5a5 a6a6 a7a7 a8a8 a9a9 a 10 a 11 b 0,0 (a 0 )b 0,1 (a 1 )b 0,2 (a 2 )b 0,3 (a 3 ) b 1,0 (a 4 )b 1,1 (a 5 )b 1,2 (a 6 )b 1,3 (a 7 ) b 2,0 (a 8 )b 2,1 (a 9 )b 2,2 (a 10 )b 2,3 (a 11 ) Number of columns of array B = Number of node disjoint paths

8 Proposed Method: Uncorrelating the bits LFSRs primarily used in circuit testing to produce pseudo-random patterns A different LFSR chosen for each sub-message i Characteristic polynomial and t i are encoded and appended to the outgoing sub-message Example of an LFSR with k = 3 and T =

9 Proposed Method: Encryption Scheme For i=0 to m-1 X i = b i,0 XOR b i,1 XOR…XOR b i,2n-1 For i=0 to m-1 For j=0 to 2n-1 C i,j = X i XOR b i,j

Globecom 0510 Proposed Method Sub-messages are routed through node disjoint routes Routes only need to be node disjoint due to the use of directional antennas A mote can overhear transmission if and only if it is within transmission range and in angular span of sending node

Globecom 0511 Proposed Method: De-uncorrelation and decryption Scheme Procedure decode For i=0 to m-1 X i = c i,0 XOR c i,1 XOR…XOR c i,2n-1 For i=0 to m-1 For j=0 to 2n-1 b i,j = X i XOR c i,j Sub-messages reverse uncorrelated in a similarly designed LFSR

12 Hardware Overhead The hardware requirements are: An m bit LFSR Two levels of XOR gates One level is used for encryption and the other is used with the LFSR Three levels of multiplexers 2x1 multiplexers at the inputs of XOR gates 4nx2n multiplexers to initiate LFSR

13 Experimental Results: Area and power requirements Power consumption of RSA chip is in the order of 500 mW Power and area of ECC module is over 300 mW and 24,000 square microns Security module designed and synthesized in VHDL for a 512 bit ckt Power consumption 5 micro Watts Area less than 25 square microns

14 Experimental Results: Performance measurements using OPNET Experiments conducted on networks of 60, 70, 80, 90 and 100 motes with 90 degree directional antennas Wireless transmission range set to 25 meters

15 Experimental Results: One intruder Experiments ran 10 times for each network size. In each run, a random node chosen as intruder Number of paths = maximum even number of node disjoint paths Used destinations at least two hops away No single intruder node was able to intercept a complete message

16 Experimental Results: Multiple intruders 70 motes # intruders# of disjoint paths 246max Percentage of messages intercepted for different numbers of paths As the number of paths increases, the number of intercepted messages decreases

17 Experimental Results: Performance of scheme in presence of several intruders # motes# paths# intruders Percentage of messages intercepted in the presence of different numbers of collaborating nodes Low interception rates even for large number of intruders

18 Conclusions An encryption method and uncorrelation scheme for secure message transmission in sensor networks Experimental results show Low resource requirements of proposed method Efficiency of proposed method in protecting secrecy of messages

19 Questions? Thank you