1. A key agreement protocol using mutual Authentication for Ad-Hoc Networks IEEE 2005 Authors : Chichun Lo, Chunchieh Huang, Yongxin Huang Date : 2005_11_29 Presented by Fei-Yau, Hung

2. Outline Introduction Review of the Huang-Chang Scheme The proposed scheme Security analysis Conclusion

3. Introduction Wireless technology has become more pervasive as E-Commerce and other applications communication platform. Two kinds of network structures in wireless area network  Infrastructure  Infrastructureless

4. Introduction Properties concerned for security design in MANET (Ad-Hoc network) :  Self-organize  Fully decentralized  Dynamic topology  Low computation power

5. Review of the Huang-Chang Scheme Notations

6. Review of the Huang-Chang Scheme Notations

7. Review of the Huang-Chang Scheme Tree structure illustrates the membership

8. Review of the Huang-Chang Scheme Key initiation phase

9. Review of the Huang-Chang Scheme Authenticating the legal children

10. Review of the Huang-Chang Scheme Session Key Generation phase

11. Review of the Huang-Chang Scheme The flows of Huang-Chang’s Scheme  The replay attack : attacker collects multiple pairs, while the group is establishing.  The password guessing attack  Performance : must repeat n times to compute for each member

12. The proposed scheme Key initiation phase

13. The proposed scheme Key initiation phase

14. The proposed scheme Session key generation phase

15. Example

17. Node11 broadcast Node1 broadcast

18. Example All members compute their own session key, and send to the checker. Finally, the checker will check all member’s session key.

19. The proposed scheme Session key Update periodically

20. Security analysis Dynamic key agreement protocol requirements  Group key secrecy  Key independency  Forward and backward secrecy

21. Security analysis Compare with Huang & Chang’s scheme  This protocol using nonce value to prevent the replay attack.  Password guessing attack does not wok.

22. Security analysis Performance Discussion MethodsG-DH2 Hypercub e DH-LKH Huang & Chang The proposed scheme Roundsnlogn logn+13logn+3 Multicast messages 10logn23 Unicast messages n-1nlogn03n-44n-7 Message size grows YNYYN DH key exchange n(logn)/2logn-100 Computation If i<n (i+1)EXP If i = 1 nEXP If i<=n (logn)EXP If i<=n (logn+1)EXP If i<n 3H+1E+1D+4X If i=n 1H+(n-1)E+2X If i<n 2H+4E+4D+3X If i=n 1H+1E+1D+1X

23. Conclusion Adding mutual authentication to avoid replay attack. Modifying transcripts to prevent password guessing attack. Periodical session key updating makes the ciphertext or chosen plaintext attack have no chance to happen. The system can work well in the MANET environment.