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Random Key-Assignment for Secure Wireless Sensor Networks

Random Key-Assignment for Secure Wireless Sensor Networks. Roberto Di Pietro, Luigi V. Mancini and Alessandro Mei. Sensor nodes. Limited memory Limited computational power Limited energy. Secure microcontroller. Threat Model. Passive attacks Cipher text attacks Active attacks

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Random Key-Assignment for Secure Wireless Sensor Networks

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  1. Random Key-Assignment for Secure Wireless Sensor Networks Roberto Di Pietro, Luigi V. Mancini and Alessandro Mei

  2. Sensor nodes • Limited memory • Limited computational power • Limited energy

  3. Secure microcontroller

  4. Threat Model • Passive attacks • Cipher text attacks • Active attacks • Take control of a sensor node • Unfriendly environment • Nodes only trust themselves

  5. Goals • Secure pairwise communication • Memory efficient • Energy efficient • Tolerate the collusion of a set of corrupted sensors

  6. Naïve solutions • Have one master key • Can’t tolerate nodes being taken over • Each node stores a seperate key for every other node • Requires too much space • Expensive to add more nodes later • Tradeoff • Use less memory, but have only a probabilistic tolerance to nodes being taken over

  7. Requirements • One way hash function • Symmetric encryption • Keyed hashed function • Pseudo-random number generator

  8. The direct protocol • A key deployment scheme • A key discovery procedure • A security adaptive channel establishment procedure

  9. Key deployment Method used in A key-management scheme for distributed sensor networks: • A pool of P random keys is generated • Each sensors takes k random keys from the pool

  10. Inefficient key discovery • Challenge is encrypted using each key and then broadcasted • Needs to perform k^2 decryptions on receiver side and k encryptions on the sender side • At least k messages have to be sent

  11. Key deployment II • Also used in A key management scheme for distributed sensor networks • Instead of challenge response, submit the indexes • Less secure, as a smart attacker can easily find the nodes that have the key it wants

  12. Key deployment III Method used in Establishing pair-wise keys for secure communication in ad hoc networks: A probabilistic approach: • A pool of P random keys is generated • k indexes into the pool are created pseudo-randomly with a publicly known seed dependent on the node id. • Less secure than challenge-response, but can be improved

  13. Channel existence

  14. Channel establishment • Find out which keys are shared and xor them together • An attacker needs to know all shared keys

  15. Corruption probability – P=1000

  16. Corruption Probability – k=120

  17. The cooperative protocol

  18. The C set • Nearby sensors • Weaker against geographically attacks • Random • Larger communication overhead • Individual properties • More trusted nodes can give higher security

  19. Upper bound • They give an upper bound on the probability that the channel between two nodes is corrupted, given w corrupted nodes

  20. Features of cooperation protocol • Sensor failure resistent • Can add more sensors if required • No information leakage • Sensors in the C set only transmits hash values of their keys • Adaptiveness • If an upper bound of w is known, C can be chosen to secure communication with a desired probability. • Load balance • a sends c+1 message, sensors in C send 1, tot=2c+1 • Only done once during setup

  21. DoS Attacks of Malicious Cooperators • Sensor doesn’t respond • After timeout, node a can pick another node • Sensor sends correct key • Lowers security • Sends false key • Can pick another C set • Notify trusted base-station • Aware that network is under attack

  22. Authentication • If node a has the keys that node a should have, according to the pseudo-random number generator, it’s probable that a is a.

  23. P=1000 and w=8

  24. P=1000 w=16

  25. P=10000 w=32

  26. Efficient and Secure Pre-deployment (ESP) • M = {} • for all keys k in P • z = RND(id||k) • if(z%(|P|/m)==0) • put k into M • |M| must be less than memory size but larger than the security constraints • Discard ID if conditions not satisfied

  27. Generated IDs

  28. Direct protocol

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