1. SPEAKER: HONG-JI WEI DATE: 2012-12-28 Secure Anonymous Authentication Scheme with Roaming for Mobile Networks

2. Outline 1 1. Introduction 2. Review of Kim et al.’s Scheme 3. Weakness of Kim et al.’s Scheme 4. Our Improved Scheme 5. Security Analysis 6. Conclusion

3. 1. Introduction (1/2) 2 Mun et al. proposed an anonymous authentication scheme with roaming for mobile networks in February, 2012. Unfortunately, Kim et al. pointed out that Mun et al.'s scheme contains two weaknesses which is replay attack and man-in-the-middle attack in July, 2012. In order to improve these weaknesses, they proposed an improved roaming authentication scheme with anonymity.

4. 1. Introduction (2/2) 3 In this paper, we analyze Kim et al.’s scheme and point out the weakness in existence. At the same time, we also propose an enhanced roaming authentication scheme to overcome the weakness of Kim et al.’s scheme.

5. 2. Review of Kim et al.’s Scheme (1/5) 4 Notations of Kim et al.'s scheme MUMobile User FAForeign Agent HAHome Agent PW X Password of an entity X ID X Identity of an entity X h(.)One-way hash function N/N'Random nonce of current session / Random nonce of next session ⊕ Exclusive OR operation ||Concatenation operation fKfK MAC generation function by using key K K XY Session key between entity X and Y PRNG(.)Pseudo Random Number Generator

6. 5 This scheme contains three main phases 1. Registration 2. Authentication and key establishment 3. Update session key 2. Review of Kim et al.’s Scheme (2/5) Notations of Kim et al.'s scheme E K /D K Symmetric Encryption/Decryption with key K PPassword of mobile user xSecret key of HA yRandom nonce generates for each mobile user

7. 6 Registration 2. Review of Kim et al.’s Scheme (3/5) MUHA Secure Channel

8. 7 Authentication and key establishment 2. Review of Kim et al.’s Scheme (4/5) MUFAHA

9. 8 Update session key 2. Review of Kim et al.’s Scheme (5/5) MU FA

10. 3. Weakness of Kim et al.’s Scheme (1/3) 9 The weakness of Kim et al.'s scheme can be found in two phases. 1. Authentication and establishment of session key 2. Update session key

11. 10 Authentication and establishment of session key 3. Weakness of Kim et al.’s Scheme (2/3) MUFAHA Replay attack

12. 11 Update session key 3. Weakness of Kim et al.’s Scheme (3/3) MU FA Replay attack

13. 4. Our Improved Scheme (1/3) 12 Registration MUHA Secure Channel

14. 13 Authentication and establishment of session key 4. Our Improved Scheme (2/3) MUFA HA

15. 14 Update session key 4. Our Improved Scheme (3/3) MU FA

16. 5. Security Analysis (1/3) 15 Authentication and establishment of session key MUFA HA Replay

17. 16 5. Security Analysis (2/3) Update session key MU FA Replay

18. 17 5. Security Analysis (3/3) Comparison table

19. 6. Conclusion (1/1) 18 In this paper, we propose an enhanced anonymous scheme to improve the weakness of replay attack in Kim et al.'s scheme. From the security analysis, we can know that our scheme indeed can prevent the replay attack in Authentication and establishment of session key and update session key phases.

20. 19 Many thanks for your listening Q & A