1. Wireless Network Keys Management What is WSN ? Steven Du ID: 3880740. CSI 5148

2. Wireless Network Keys Management Communication Security between sensor node Because of memory and computation constraint in WSN use symmetric keys for encryption and decryption  sensors use common shared key to encrypt and decrypt  common shared keys are pre-distributed or computed by specific scheme The Globus Toolkit 4 Programmer's Tutorial Borja Sotomayor, University of Chicago, Department of Computer Science. Copyright © 2004, 2005 Borja Sotomayor

3. Wireless Network Keys Management Key establishment schemes Definition of key establishment: The algorithm or method for sensors to setup (or exchange) their common shared key for communication data Main requirements on key establishment schemes: 1.Availability : The network service is available without limitation with key establishment 2.Authenticity: Ability for verifying that the message sent by a node is authentic. 3.Confidentiality : The key establishment technique should protect the disclosure of data to unauthorized parties. 4.Integrity : No falsification of data during transmission. Key Pre-distribution in Wireless Sensor Networks when Sensors are within Communication Range Sushmita Ruj, Amiya Nayak and Ivan Stojmenovic

4. Wireless Network Keys Management WSN symmetric key establishment steps: 1.Key pre-distribution: Preload keys into each sensor nodes before WSN deployment. 2.Shared-key discovery: Setup connection between two sensor nodes in their communication range by finding common shared key. 3.Path-key establishment : establishment of communication path and path key between two unconnected sensor nodes. Path: linked nodes chain between two nodes without direct connection Path key: Common shared key used by the linked nodes in path to transfer message B S E C F D K G Key sb Key be Key bc Key SD Key ef Key fg Key gd Key kd Key fk

5. Wireless Network Keys Management WSN symmetric key establishment steps: 1.Key pre-distribution: Preload keys into each sensor nodes before WSN deployment. B S E C F D K G {2, 3, 4, 5, 9} {5, 7, 4, 9 1} {3, 8, 1, 0 7} {6,2, 8, 9 0} {3 7, 9, 2, 4} {5, 7, 4, 9 1} {9, 2, 6, 3 1} {1, 6, 4, 7 8}

6. Share key ? Wireless Network Keys Management WSN symmetric key establishment steps: 2. Shared-key discovery: Setup connection between two sensor nodes in their communication range by finding common shared key. B S E C F D K G {2, 3, 4, 5, 9} {5, 7, 4, 9 1} {3, 8, 1, 0 7} {6,2, 8, 9 0} {3 7, 9, 2, 4} {5, 7, 4, 8, 4} {9, 2, 6, 3 1} {1, 6, 4, 7 8} Share key ?

7. no ! Wireless Network Keys Management WSN symmetric key establishment steps: B S E C F D K G {2, 3, 4, 5, 9} {5, 7, 4, 9 1} {3, 8, 1, 0 7} {6,2, 8, 9 0} {3 7, 9, 2, 4} {5, 7, 4, 8, 4} {9, 2, 6, 3 1} {1, 6, 4, 7 8} Yes, 4,9 Yes 8 Yes 4,7 2. Shared-key discovery: Setup connection between two sensor nodes in their communication range by finding common shared key. Yes 1,7

8. Wireless Network Keys Management WSN symmetric key establishment steps: 3. Path-key establishment : establishment of communication path and path key between two unconnected sensor nodes. B S E C F D K G {2, 3, 4, 5, 9} {5, 7, 4, 9 1} {3, 8, 1, 0 7} {6,2, 8, 9 0} {3 7, 9, 2, 4} {5, 7, 4, 8, 4} {9, 2, 6, 3 1} {1, 6, 4, 7 8} 4, 5, 9 8 4, 7 1,7

9. Wireless Network Keys Management WSN symmetric key establishment steps: B S E C F D K G Key sb Key be Key bc Key SD Key ef Key fg Key gd Key kd Key fk 3. Path-key establishment : establishment of communication path and path key between two unconnected sensor nodes.

10. Wireless Network Keys Management WSN symmetric key establishment steps: 1.Symmetric key establishment with Polynomial in finite field. B S E C F D K G Id =7 I8 = 9 Id = 9 Id = 15 Id = 3 Id = 9 Id = 11 Id = 13

11. Wireless Network Keys Management WSN symmetric key establishment steps: 1.Symmetric key establishment with Polynomial in finite field. B S E C F D K G Id =7 I8 = 9 Id = 9 Id = 15 Id = 3 Id = 9 Id = 11 Id = 13 What is common key ?

12. Wireless Network Keys Management WSN symmetric key establishment steps: B S E C F D K G Id =7 I8 = 9 Id = 9 Id = 15 Id = 3 Id = 9 Id = 11 Id = 13 What is common key ? 1.Symmetric key establishment with Polynomial in finite field.

13. Wireless Network Keys Management WSN symmetric key establishment steps: B S E C F D K G Id =7 I8 = 9 Id = 9 Id = 15 Id = 3 Id = 9 Id = 11 Id = 13 What is common key ? 1.Symmetric key establishment with Polynomial in finite field.

14. Wireless Network Keys Management WSN symmetric key establishment steps: 1.Symmetric key establishment with Polynomial in finite field. Each node can make security communication with other nodes in its communication range

15. Wireless Network Keys Management Triple Key Distribution What is triple key distribution?  a common key discovery scheme among 3 sensor nodes Y X Z Common triple shared key Y X Z

16. Wireless Network Keys Management Triple Key Distribution Why triple key distribution?  path key establishment  verifying the relayed message in path is authentic  detect fault/ malicious nodes K{s, c, b} BSCDK Key SCKey BKKey CBKey KD K{c, b, k} K{b, k, d}

17. Wireless Network Keys Management Triple Key Distribution How triple key is distributed?  any three full connected nodes share an unique common key  any three string connected nodes share an unique common key Two schemes: A.full connected triple keys distribution B.String connected triple keys distribution

18. Wireless Network Keys Management Triple Key Distribution (full connected triple nodes) Triple nodes that share an unique triple key: BCS, BCE, ECK, EFK, FGK, DGK Y X Z Common triple shared key B S E C F D K G Key sb Key be Key bc Key SD Key ef Key fg Key gd Key kd Key fk Key be Key EK Key KG Key CS

19. Wireless Network Keys Management Triple Key Application (full connected triple nodes) K{s, e, c} BS E C F DK G Key SC Key SE Key CG Key BG Key BKKey CBKey KD Key bc Key GK Key EBKey FD Key EC Key FK K{c, e, b}K{b, f, k}K{k, f, d} K{c, b, g} K{b, k, g} C compare the message relayed by B to the sent message. Are they same? Yes? Done! No? Node B is in trouble, report!

20. Wireless Network Keys Management Triple Key Distribution (String connected triple nodes) B S E C F D K G Key sb Key be Key bc Key SD Key ef Key fg Key gd Key kd Key fk Key be Triple nodes that share an unique triple key: SBEBCKCEFEFKFGDKDGEFG SBC BEFCKFECKFKDCKDKFG Y X Z Common triple shared key

21. Wireless Network Keys Management Triple Key Application (String connected triple nodes) K{s, c, b} BSCDK Key SCKey BKKey CBKey KD K{c, b, k} K{b, k, d}

22. Wireless Network Keys Management Triple Key Application (String connected triple nodes) K{s, c, b} BSCDK Key SCKey BKKey CBKey KD K{c, b, k} K{b, k, d} C: does node B correctly transfer my message to node K? C compare the message relayed by B to the sent message. Are they same? Yes? Done! No? Node B is in trouble, report!

23. Wireless Network Keys Management Analysis of triple key scheme Security analysis: a compromised intermediate node possibly refuses or relay fake data frame. Because of acknowledge mechanism, its behaviour is monitored, found and kicked out of the network. SYD Key {?, S, Y}Key {S, Y, D} Does node Y relay my message? No  node Y stopped work, broadcast to whole WSN Yes  compare the relayed message. is the relayed message same as I sent? No  node Y is compromised, broadcast to kick off Y

24. Wireless Network Keys Management Several possible triple key establishment algorithms Symmetrical polynomial for triple key computation x, y, z are the ID of each node in the triple nodes X=10, y=11, z=12  85186

25. Wireless Network Keys Management Triple key management in WSN? a)A wireless sensor network with n nodes b)The possibility for any two nodes to setup direct link is p c)Possible average number of triple keys in each node S full connected triple nodes String connected triple nodes

26. Wireless Network Keys Management Triple key in cluster based network

27. Wireless Network Keys Management Triple key in cluster based network WSN network nodes density = D Deployment area = S Communication radius = r Cluster based WSN Number of cluster headers C is a constant number, describes the WSN nodes deployment overlap level >1 Average nodes number in one cluster Suppose the possibility of link between any two nodes in same cluster is P, we have:

28. Wireless Network Keys Management Triple key in cluster based network string connected triple nodes Average number of triple keys for each node