1. An Enhanced Two-factor User Authentication Scheme in Wireless Sensor Networks DAOJING HE, YI GAO, SAMMY CHAN, CHUN CHEN, JIAJUN BU Ad Hoc & Sensor Wireless Networks 2010 Vol. 0, pp. 1–11 Citation: 14 Presenter: 林致良 Date: 2013/4/22 1

2. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 2

3. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 3

4. Introduction In WSNs, both Gateway (GW) nodes and external parties (users) are able to access directly the real- time data from the sensor nodes. A two-factor authentication is a concept used to describe an authentication mechanism, where more than one factor is required to authenticate the communicating party. 4

5. Introduction 5

6. This paper points out: Security weaknesses in Das M.’s scheme such as suffering from insider attack. This paper presents : An enhanced two-factor user authentication protocol. 6

7. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 7

8. Related work Das M.'s scheme consists of two phases: 1. Registration phase 2. Authentication phase (1) Login phase (2) Verification Phase 8

9. 9 Das M.'s scheme GW node Compute symmetric key: K one-way hash function: h( ⋅ )

10. Related work Das M.'s scheme consists of two phases: 1. Registration phase 2. Authentication phase (1) Login phase (2) Verification Phase This phase is invoked when User wants to perform some queries to or access data from the network. 10

11. 11 Das M.'s scheme GW node Compute:

12. Verification Phase 12 GW node (T*−T)≤ΔT Compute:

13. Verification Phase 13 GW node

14. 14 Attack on Das M.'s scheme GW node

15. Design weakness on Das M.'s scheme 15

16. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 16

17. The new proposed protocol The proposed scheme consists of three phases: 1. Registration phase 2. Authentication phase (1) Login phase (2) Verification Phase 3. Password updating phase 17

18. 18 The new proposed protocol GW node Compute: arbitrary number: b (large) secret number: K, J

19. 19 The new proposed protocol GW node Compute:

20. Verification Phase 20 GW node (T*−T)≤ΔT Compute:

21. Verification Phase 21 GW node

22. 22 Password updating phase Compute:

23. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 23

24. Security Analysis 24

25. Performance Analysis 25

26. Outline Introduction Related work The new proposed protocol Security and performance analysis Conclusion 26

27. Conclusion This paper points out the security weaknesses in a two-factor user authentication protocol for wireless sensor networks. The analysis has shown that the security issues in that scheme can be solved in a very simple way, which is the proposal in this paper. 27