1. Provably Secure Authenticated Key Agreement Scheme for Distributed Mobile Cloud Computing Services
Source : Future Generation Computer Systems, Vol. 68, pp , 2017
Authors : Vanga Odelu, Ashok Kumar Das, Saru Kumari, Xinyi Huang and Mohammad Wazid
Speaker : Hsiao-Ling Wu
Date: 2017/06/01

2. Outline Review of Tsai-Lo’s scheme Proposed scheme Security analysis
Performance analysis
Conclusions

3. Review of Tsai-Lo’s scheme (1/7)
Three phases:
SCG setup phase
Registration phase
Authentication and key establishment phase
Smart card generator (SCG)
User (Ui)
Server (Sj)

4. Review of Tsai-Lo’s scheme (2/7)
Notations

5. Review of Tsai-Lo’s scheme (3/7)
SCG setup phase
Smart card generator (SCG)

6. Review of Tsai-Lo’s scheme (4/7)
Registration phase
User (Ui)
Smart card generator (SCG)
IDi
Secure channel
Ki = (s+H1(IDi))-1∙P Ki
Secure channel
Ei = Ki ⊕ h(pwi||fi)
Store Ei on mobile device
Server (Sj)
Smart card generator (SCG)
SIDj
Secure channel
Kj = (s+H1(SIDj))-1∙P Kj
Secure channel

7. Review of Tsai-Lo’s scheme (5/7)
Authentication and key establishment phase
User (Ui)
Ei = Ki ⊕ h(pwi||fi)
Server (Sj) Kj

8. Review of Tsai-Lo’s scheme (6/7)
Service provider impersonation attack
User (Ui)
Ei = Ki ⊕ h(pwi||fi)
Attacker (A)

9. Review of Tsai-Lo’s scheme (7/7)

10. Proposed scheme(1/3)
SCG setup phase
Smart card generator (SCG)

11. Proposed scheme (2/3) Registration phase User (Ui)
Smart card generator (SCG)
IDi
( 𝜎 𝑖 , 𝜃 𝑖 ) = Gen(fi)
𝜎 𝑖 = Rep( 𝜃 𝑖 ||fi)
Secure channel
Ki,Lt = (s+H1(Idi||Lti))-1∙P Ki
( 𝜎 𝑖 , 𝜃 𝑖 ) = Gen(fi)
Ei,Lt = Ki,Lt ⊕ h(pwi|| 𝜎 𝑖 )
ei = H5(IDi||pwi|| 𝜎 𝑖 )
Store { 𝜃 𝑖 , ei, Ei,Lt, Rep(∙), t}on mobile device
Secure channel
Server (Sj)
Smart card generator (SCG)
SIDj
Secure channel
Kj = (s+H1(SIDj))-1∙P Kj
Secure channel

12. Proposed scheme (3/3) Authentication and key establishment phase
Ei,Lt = Ki,Lt ⊕ h(pwi|| 𝜎 𝑖 )
ei = H5(IDi||pwi|| 𝜎 𝑖 )
User (Ui)
Server (Sj) Kj
𝜎 𝑖 = Rep( 𝜃 𝑖 ||fi)
Checks if ei = H5(IDi||pwi|| 𝜎 𝑖 )

13. Security analysis
SCG: smart card generator; F1: whether provides user credentials’ privacy; F2 : whether provides SK-security; F3 : whether provides secure mutual authentication;
F4 : whether prevents impersonation attack; F5 : whether provides user untraceability;
F6 : whether supports for mobile user revocation.
[3] J.L. Tsai, N.W. Lo, A privacy-aware authentication scheme for distributed mobile cloud computing services, IEEE Syst. J. 9 (3) (2015) 805–815.
[33] Y.M. Tseng, S.S. Huang, T.T. Tsai, J.H. Ke, List-free ID-based mutual authentication and key agreement protocol for multiserver architectures, IEEE Trans. Emerging Top. Comput. 4 (1) (2016) 102–112.

14. Performance analysis

15. Conclusions
In this paper, the authors have first analyzed Tsai–Lo’s authentication scheme and shown that their scheme is insecure against server impersonation attack.
We have proposed an efficient provably secure mutual authentication and key agreement scheme.