The opportunity to access on-demand, unbounded computation and storage resources has increasingly motivated users to move their health records from local data centers to the cloud environment. This change can reduce the costs associated with the management of data sharing, communication overhead and improve Quality of Service (QoS). Processing, storing, hosting and archiving data related to e-Health systems without physical access and control can exacerbate authentication and access control issues in this new environment. Therefore, convincing users to move sensitive medical records to the cloud environment requires implementing secure and strong authentication and access control methods to protect the data.

1. Authentication and Access Control in e-Health
Systems in the Cloud
Nafiseh Kahani, Khalid Elgazzar, James R. Cordy
School of Computing
Queen’s University, Canada

2. Outline
 Introduction
 Proposed Method
 Features and Security Risk Analysis
 Conclusion

3. Introduction
 Security and access control issues are strong barrier for users to
use Cloud computing systems
 How can we authenticate the various communicating entities?
 How can we mange access by these communicating entities?
• Traditional Access Control mechanisms

4. Proposed Scheme
Service Provider
User
AAM
Cloud Server
Data Owner

5. System Architecture and Parameters
 ID; Public Keys (AAM and CS); System Parameters
 Data is represented in n fragments (R={R1,...,Rn})
 Secret, sensitive, and official security levels based on the administrative,
medical, and accounting records
 Each fragment is encrypted with its category-specific secret key and generates
C = {C1, ..., Cn}
 Multiple keywords in the search request (encrypted searchable indexes) [1]

6. Authentication Phase
 Authentication is performed based on the secret ID that users
receive during their registration with the system
 The zero-knowledge protocol can prove the identity of the user
anonymously without revealing any knowledge

7. EncPUBAM(x, v, BDKAM, si)
EncKSCS(Data, N+1)
End
((Enc(KSA_i)(e, Time)), si+1)
((Enc(KSA_i+1)(y)), si+2)
Start…
Authentication &
Access Control
File Access
Registration{ID}
EncPUBCS(token, KSCS, N)
((Enc(KSA_i+2)(token, SFK)), si+3)

8. Access Control Phase
 Subjects and Roles
• S = {S1,...,Sn} and R = {R1,...,Rm}
 Subject Attributes
 Objects
• O = {O1, ..., On}
 Object Attributes
 Actions/Rights
• a = {a1,...,am} and α={α1,…,αn}

9. Access Control- Static
 Employ(org, Si, Rj ) [2]
 Define(org, ai,αj) [2]
 Grant(Si, org, Rj , αi, Oj )
 Grant(S, αi, Oj, is_condition)
⍱s ⍱ o ⍱ α is_access (S, α, O)
True, if Grant (S,α, O, is_condition) ∨ Grant(S, org, R, α, O)
False, otherwise

10. Access Control- Dynamic
 Using the concept “Intention” to narrow down the user rights
according to the intention per request
 Intentions presented in hierarchical relationships [3]
 Each leaf node is linked to a record:
• Trapdoor
• Rights
• Fragment

11. Authentication Management Component (AMC)
AMCInitiator Repository
Request
RSC Intention Tree
TMC
Reject
Admittable
Request
PDC
Subject Attribute
Object Attribute
Static Access Policies

12. EncPUBAM(x, v, BDKAM, si)
EncKSCS(Data, N+1)
End
((Enc(KSA_i)(e, Time)), si+1)
((Enc(KSA_i+1)(y)), si+2)
Start…
Authentication &
Access Control
File Access
Registration{ID}
EncPUBCS(token, KSCS, N)
((Enc(KSA_i+2)(token, SFK)), si+3)

13. Features and Security Risk Analysis
 Data Confidentiality
• standard symmetric-key algorithm
 Fine-grained Access Control
• two-step access control
 Non-repudiation
• Using logs
 Authentication and User Privacy
• the zero-knowledge protocol does not reveal the user ID

14. Features and Security Risk Analysis- cont’d
 Withstanding Security Attacks
• Replay Attack (sequence index, time-stamp)
• Man-in-the-Middle Attack
• Brute-force Attack
• Denial-of-Service Attack [4]

15. Conclusion
 The propose method simultaneously achieves authentication and
fine-grained access control
 The authentication process based on a zero-knowledge method,
determines authorized users
 The access control method determines user privileges to access
data

16. Thank you!

17. References
 [1] N. Cao, C. Wang, M. Li, K. Ren, and W. Lou, ”Privacy-preserving multi- keyword ranked search over
encrypted cloud data,” IEEE Transaction on Parallel and Distributed Systems, vol 25, pp. 222-233, 2014.
 [2] A. A. Kalam, R. E. Baida, P. Balbiani, S. Benferhat, F. Cuppens, Y. Deswarte, and G. Trouessin,
”Organization based access control,” in IEEE 4th International Workshop, pp. 120-131, June 2003.
 [3] J. W. Byun, E. Bertino, and N. Li, ”Purpose based access control of complex data for privacy
protection,” in Proceedings of the 10th ACM Symposium on Access Control Models and Technologies, pp. 102-110,
June 2005.
 [4] M. Fallah and N. Kahani “TDPF: A traceback-based distributed packet filter to mitigate DDoS
attacks”, Journal of Security and Communication Networks, vol 7, pp. 1-20, 2014.