SPRAHN : Secure & Protected Rewards in Ad Hoc Networks for ECE695 – Mobile Wireless Networking

1. SPRAHN: Secure & Protected Rewards in Ad Hoc NetworksforECE695 – Mobile Wireless Networking Charles D. Fico April 27th 2006

2. Introduction • Rewards have been shown to cause fair play via game theory • Compensates intermediate nodes (INs) for loss of limited resources • Battery power • CPU Time • Memory Resources

3. Introduction • SPRAHN: Secure & Protected Rewards in Ad Hoc Networks • Considers MANET as an internet link • Previous work centers on local MANET reward

4. Background - Cryptography • Three cryptographic means will be used for the secure rewards • AES-196 for Symmetric encryption • RSA for public key or Asymmetric encryption • ElGamal key agreement for key exchange

5. Background – Cryptography: AES • Advanced Encryption Standard –Rijndael • Winner of NIST standardization search • AES is a block cipher & supports • 128 bit blocks • 128, 196 or 256 bit keys. • AES key levels >= 192 bits satisfies TOP SECRET information security for decades

6. Background – Cryptography: RSA • RSA developed by Rives, Shamir and Adleman at MIT in 1977 • Based on building two exponents which are inverses modulo a composite prime N. • Recent concerns of 1024 bit key security • While 2046 bit keys are currently safe, 4096 bit provide a standard having longevity >= AES-192

7. Background – Cryptography: ElGamal • Based on Diffie-Hellman key agreement • Uses a Trusted Authority (TA) to provide public key • TA can be in the form of a signed/verified certificate

8. Background – Other Reward Systems • Deal with internal, local MANET, rewards and peer reviews • Many are unspecific about what the reward is; It is something good though • Rewards for ferrying traffic external to the network is not covered

9. SPRAHN Operation • Reward Link Initialization • Reward Link Refresh • Reward Outline • Key acquisition

10. Reward Link Initialization • Setup of the reward link establishes INs along the path from the local node to the MANET boundary node • Uses current routing algorithm active in the MANET • Major change required is memorization and propagation of boundary nodes addresses & public

11. Reward Link Initialization • Routes too & from the boundary node may change • Boundary nodes should remain the same, since they are less-mobile or non-mobile backbone attachments to external networks for the local MANET

12. Reward Link Initialization • Reward links are established internal node of the local MANET sending/receiving packets external to the local MANET • Initiated on local node preparing to send external packet or boundary node notifying of incoming external packet

13. Reward Link Initialization • In the unlikely event that a boundary node receives a packet bound for an external connection for which there is no reward link from the sender • Boundary node can issue a reward link request from the sender of the packet while suspending propagation of the packet. • Protects the network from nodes accidentally or maliciously not setting up Reward Links for packets to be sent outbound

14. Reward Link Initialization • Boundary nodes may reuse valid reward links with local MANET node same for different external nodes. • Allows for decrease in network overhead • Via public key encryption between internal and boundary nodes, an AES-192 encryption key is agreed upon for subsequent exchange of data packets for the reward link

15. Reward Link Refresh - Rewards • Local node in MANET connected with reward link is responsible party • Keep alive messages contain number of inbound & outbound messages sent, time stamp and sequence number. • Keep alive messages are AES-192 encrypted

16. Reward Link Refresh - Route • Based on active mobility (rate of route breaks) dictate local nodes boundary node route refreshes • Just as in reward link initialization but noted as an reward link update

17. Reward Outline • Nodes entering network receive boundary node list • Node that entered network notifies/registers with a boundary node via a time stamped login message encrypted with the boundary nodes public key • Node is ready to start collecting unused rewards and gain new rewards

18. Reward Outline • Based on weighted number of packets • Packet weight is determined by size • Downstream & Upstream packets are counted

19. Reward Outline • Maximum bandwidth for bonus is double normal bandwidth • Nodes are priority rated on size of unused reward • Reward collectable based on % of network load

20. Key Acquisition • New Node – one which has never acquired reward specifications on this network before; node requiring clean start • New node should be able to participate ASAP • Needs public key for itself

21. Key Acquisition • Upon entering MANET boundary node information/address will be supplied • New node connects with a boundary node to subscribe for reward membership and receives boundary nodes certificate • Use ElGamal based key acquisition with public key from boundary certificate

22. Key Acquisition • Boundary node propagates information to other boundary nodes via a common AES-192 key which was exchanged via boundary node public keys

23. Conclusion • SPRAHN: Secure & Protected Rewards in Ad Hoc Networks • Rewards are based on traffic too and from external sources • Rewards are bandwidth specific

24. References • C. D. Fico, “SPRAHN: Secure & Protected Rewards in Ad Hoc Networks”, IUPUI, IN, April, 2006 • Y. Zhang, W. Lou, and Y. Fang, “SIP: A Secure Incentive Protocol against Selfishness in Mobile Ad Hoc Networks”, IEEE Communications Society, WCNC, 2004. • P. Engelstad, D. V. Thanh, and G. Egeland, “Name Resolution in On-Demand MANETs and over External IP Networks”, Univ. of Oslo, United Kingdom. • Qi He, D. Wu, and P. Khosla, “SORI: A Secure and Objective Reputation-based Incentive Scheme for Ad-hoc Networks”, Carnegie Mellon Univ., Dept. of Electrical & Computer Engineering, Gainesville, FL 32611. • J. Pieprzyk, T. Hardjono, and J. Seberry, “Fundamentals of Computer Security”, Springer-Verlag Berlin Heidelberg, 2003. • Wikipedia – Advanced Encryption Standard, http://en.wikipedia.org/wiki/Advanced_Encryption_Standard. • Wikipedia – RSA, http://en.wikipedia.org/wiki/RSA. • Wikipedia – ElGamal encryption, http://en.wikipedia.org/wiki/ElGamal

25. More Questions??