1. Hybrid Cloud Architecture for Software-as-a-Service Provider to Achieve Higher Privacy and Decrease Securiity Concerns about Cloud Computing
P. Reinhold et al
지능형 시스템 연구실
문성필

2. Outline Introduction Cloud Model Comparison Hybrid Cloud Architecture
Implemented Prototype
Conclusion

3. Introduction
The increasing knowledge about cloud computing technology and its publicity leads to a growing number of service offerings over the
Internet
Even small and medium sized companies are able to offer services
through cloud computing concepts
Resource can be obtained easily from public cloud providers
e.g. Amazon Web Services, Instagram

4. Introduction Many of these cloud services are provided in a form of
Software-as-a-Service (SaaS)
The high acceptance of these services suggests that private consumers have a lower privacy demand than
business users
Typical reasons are security and privacy
This paper propose a hybrid cloud architecture
enhanced with an additional architecture layer
between business logic and persistence layer
It has minimal migration effort and reveals
no information, except for meta data

5. Cloud Model Comparison
The table shows a comparison between the 3 cloud service models
Privacy is low for public and medium for private cloud
Private clouds have strong authorization and access control
But, there is no special requirement to secure data
The cloud provider often has access to customer data

6. Cloud Model Comparison
The table shows a comparison between the 3 cloud service models
Data-at-rest encryption is possible in all of the models
But, strongly connected with key ownership and management
If the same istance encrypts data and stores the referring key, that is not trustable security

7. Hybrid Cloud Architecture
The aim of this paper is to combine the security of a private cloud and availability of a public cloud
This paper proposed privacy-enhanced hybrid cloud architecture

8. Hybrid Cloud Architecture
The architecture of this paper use AES for encryption
The result of test about encryption algorithms, AES works most efficient

9. Hybrid Cloud Architecture
Key concept
The master key kM
The master key is persisted by consumer
The master key is used to encrypt / decrypt the data keys
The data key dxky
The data keys are persisted by the provider
The data keys are used to encrypt / decrypt data
The transfer key kT
The transfer key are generated during the customers registration
The transfer key are used for secure exchange of a temporary copy of the consumers’ master key

10. Hybrid Cloud Architecture
The consumer uses a computer with Internet connection to access the SaaS
The consumer has a master key for encryption

11. Hybrid Cloud Architecture
The initial login and identification procedure should be located on
physically separated hardware or be outsourced to a trusted ID
verification provider

12. Hybrid Cloud Architecture
The key management system, storing encryption keys, is another
security critical resource and should not be integrated in the private
cloud

13. Hybrid Cloud Architecture
The private cloud structures contain the application server layer and encryption server layer

14. Hybrid Cloud Architecture
All communication pass these tiers, so they have to be highly scalable
The public cloud provider is illustrated in form of a persistence layer

15. Hybrid Cloud Architecture
Security Overview
After a successful login, the consumer allows the provider to decrypt the data keys dxky with its master key kM
The data keys allow decrypting the data stored in the public cloud
This method makes the consumer and SaaS provider trust the public cloud provider in next three scenario

16. Hybrid Cloud Architecture
Threat Scenario A
An attack against the public cloud provider
Even if the attackers have full access to resources of the cloud provider, all data are secure
Attack!

17. Hybrid Cloud Architecture
Threat Scenario B
An attack against the SaaS provider
If SaaS provider is attacked, the attacker gets no access to consumer data
Because the attacker can’t decrypt data keys
Attack!

18. Hybrid Cloud Architecture
Threat Scenario C
An attack against the consumer
The attacker obtains the login credentials, factors and the master key
But the attacker can’t access to other consumer’s data
Application servers of different consumers should be at least virtually separated
Attack!

19. Implemented Prototype
The private cloud servers
Environment
OpenNebula 4.4
CPU
3 GHz Dual-Cores
RAM
8 GB
Key Management
VM (Virtual Machines)
Load balancing
Jboss mod_cluster 1.2.6
Gateway
Apache http-Server

20. Implemented Prototype
Client and server
http POST requests for file uploads
http GET requests for file downloads
The client send SQL Queries to test the DB capability

21. Implemented Prototype
Test Setup
Started with a delay of 20s, send files
While one client sends SQL queries
Two file clients work after the following patterns
ABABA
A : UDD (upload, download, delete) 12 files of 1MB, 2s delay
B : UDD 12 files of 1MB, 10ms delay
Third client work after the following patterns
CDC
C : UDD 5 files of 10MB, 5s delay
D : UDD 3 files of 10MB 10ms delay
The simulated clients take 10m 23s

22. Implemented Prototype
Test Results
The result shows the percentage of times of each works to upload / download files to cloud
The encryption and decryption times compared to upload / download times are so small

23. Conclusion
Hybrid cloud architecture offers compromise for multiple reasons
The solution addresses SME with experience in SaaS and own hardware infrastructure
This model offers a higher security level and lowers privacy concerns of consumers
The prototype includes scalable and flexible encryption servers
With minimal key management system