1. 網路環境中通訊安全技術之研究 Secure Communication Schemes in Network Environments
博士論文
指導教授：張真誠 博士 (Dr. Chin-Chen Chang)
研究生：李佳穎 (Chia-Yin Lee)
Department of Computer Science and Information Engineering
National Chung Cheng University, Chia-Yi, Taiwan

2. Outline Introduction A Mutual Authenticated Key Agreement Scheme
A Dynamic ID-based User Authentication Scheme Using Smart Cards
A Secure Single Sign-on Mechanism for Distributed Computer Networks
An Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET
A Secure Protocol for Mobile Devices
Conclusions and Future Works

3. Introduction (1/2) Property of network environments convenient
efficient
cannot communicate face to face
insecure
Secure communications
user authentication
data confidentiality

4. Introduction (2/2) Authentication user authentication protocols
mutual authentication protocols
Confidentiality
encryption
session key establishment protocols

5. Mutual Authenticated Key Agreement (1/6)
Login into the server over insecure networks:

6. Mutual Authenticated Key Agreement (2/6)
Drawbacks of conventional user authentication schemes
suffer from possible attacks, (e.g., forgery attacks)
require high computational costs to provide high security (e.g., modular exponentiation)
extra time-synchronized mechanisms are needed (using timestamp)
do not establish a one-time session key

7. Mutual Authenticated Key Agreement (3/6)
A secure authenticated key agreement protocol:
direct authentication
no timestamps
perfect forward secrecy

8. Mutual Authenticated Key Agreement (4/6)
Initialization phase:
(Secure Channel) Ui
Server

9. Mutual Authenticated Key Agreement (5/6)
Authentication phase:

10. Mutual Authenticated Key Agreement (6/6)
Comparison:
Security properties
Ours
Lee et al.’s 2005 [62]
Chien et al.’s 2004 [24]
Sun’s 2000 [87]
Lamport’s 1981 [55]
No password table
Yes No
Withstanding the replay attack
Withstanding the parallel session attack
Mutual authentication
Passwords chosen by the users freely
Not requiring time synchronization
One-time session key establishment

11. A Dynamic ID-based User Authentication Scheme Using Smart Cards (1/5)
Conventional authentication schemes
the log-in identity (ID) is never change
the adversary can trace the source of the sender
Existing dynamic ID-based user authentication schemes
suffer from possible attacks
must maintain a registration table

12. A Dynamic ID-based User Authentication Scheme Using Smart Cards (2/5)
The characteristic of our method
no registration table
without using timestamps
ensure the privacy of the users
achieve perfect forward secrecy

13. A Dynamic ID-based User Authentication Scheme Using Smart Cards (3/5)
Registration phase:

14. Authentication phase:

15. A Dynamic ID-based User Authentication Scheme Using Smart Cards (5/5)
Comparison of security properties:
Items
Das et al.’s 2004 [26]
Wang et al.’s 2009 [97]
Khan et al.’s 2010 [44]
Ours
Mutual authentication No
Yes
Password chosen by users
User anonymity
Without registration table
Withstand impersonation attacks
Without time-synchronized mechanisms
Session key establishment
Perfect forward secrecy
No*
* Since Das et al.’s and Wang et al.’s schemes do not provide session key establishment, these two schemes do not provide the property of perfect forward secrecy for transmitted messages.

16. A Secure Single Sign-on Mechanism for Distributed Computer Networks (1/6)
Conventional authentication schemes
register with each service provider
keep different identity/password pairs
Existing user identification schemes for distributed networks
suffer from possible attacks
require time-synchronized mechanisms

17. A Secure Single Sign-on Mechanism for Distributed Computer Networks (2/6)
The characteristic of our method
withstand possible attacks (e.g., impersonation attacks)
without time-synchronized mechanisms
more efficient

18. A Secure Single Sign-on Mechanism for Distributed Computer Networks (3/6)
Registration phase:

19. User identification phase:

20. A Secure Single Sign-on Mechanism for Distributed Computer Networks (5/6)
Computation cost comparison:

21. A Secure Single Sign-on Mechanism for Distributed Computer Networks (6/6)
Communication cost comparison:

22. Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET (1/6)
Existing schemes
adopt asymmetric and symmetric cryptosystems
use timestamps
suffer from possible attacks
do not provide the property of anonymity

23. Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET (2/6)
The characteristic of proposed scheme
use low cost functions
without time-synchronized mechanisms
provide anonymity for mobile users
the session key selected by the mobile user

24. Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET (3/6)
Registration phase:

25. Authentication and key establishment phases:

26. Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET(5/6)
Performance comparisons:

27. Enhanced Authentication Scheme with Anonymity for Roaming Service in GLOMONET (6/6)
Functionality comparisons:

28. A Secure E-mail Protocol for Mobile Devices (1/8)
systems
a popular medium for data transmission
transmit pure text and multimedia
Internet is public and insecure
data might be eavesdropped
If long-term secret key is compromised
all previous mails might be exposed

29. A Secure E-mail Protocol for Mobile Devices (2/8)
Objectives of our research
reduce the computation cost
achieve Perfect Forward Secrecy (PFS)
work in the inter-domain

30. A Secure E-mail Protocol for Mobile Devices (3/8)
Registration phase:

31. A Secure E-mail Protocol for Mobile Devices (4/8)
Login phase:

32. A Secure E-mail Protocol for Mobile Devices (5/8)
The first sub-phase of the sending phase:

33. The second sub-phase of the sending phase:

34. A Secure E-mail Protocol for Mobile Devices (7/8)
The receiving phase:

35. A Secure E-mail Protocol for Mobile Devices (8/8)

36. Conclusions and Future Works (1/2)
We have proposed solutions as follows
mutual authenticated key agreement protocol
dynamic ID-based user authentication scheme
secure single sign-on mechanism for distributed computer networks
authentication scheme with anonymity for roaming service
secure protocol for mobile devices

37. Conclusions and Future Works (2/2)
In the future, we will extend the result of this study
decrease the overhead of message transmission
design authentication schemes that can provide 1-out-of-∞ deniability
design secure authentication protocols in the RFID systems