1. “Ensuring distributed accountability for data sharing in the cloud”
Smitha Sundareswaran, Anna C. Squicciarini and Dan Lin

2. Contents Cloud computing Introduction to CIA framework
Problem statement
Information accountability
Automated logging mechanism
End-to-end auditing mechanism
Security discussion
Performance study
Conclusion
References

3. Cloud computing

4. Introduction to CIA framework
Security of user data in cloud computing
Cloud computing & its services
User’s data processed in remote machine
Fear of losing data & other security concerns
Cloud Information Accountability(CIA) framework
Highly decentralized
We leverage JAR programmable capabilities
Also use distributed auditing mechanisms

5. Problem statement
Cloud user send his/her data & access control policies to the service provider
The service provider will have granted access rights
If the rights are granted using conventional access control mechanisms, data will be fully available at the service provider
We use new logging and auditing techniques to track the actual usage of data

6. Requirements The logging technique must satisfy:
Logging should be decentralized
Every access to user’s data should be automatically logged
Log files should be reliable and tamper proof
Recovery mechanisms are also desirable
Log files should sent back to data owners periodically

7. Information accountability
Accountability helps to
Trace the user’s data
Protect sensitive & confidential information
Enhance user’s trust in cloud computing
A cloud is accountable if:
Faults can be reliably detected
Each fault can be linked to one party (customer or provider)

8. Accountable clouds

9. Major components of CIA framework
Logger
Have logging access to a particular instance of user data
Encrypt log record using the public key of the content owner
Periodically send the log record to log harmonizer
Ensure access & usage control policies associated with data are honored
Generate the error correction information for each log record
Log harmonizer
Responsible for auditing: Two strategies:
Push strategy
Pull strategy
Responsible for handling log file corruption

10. Accountability mechanism

11. Data flow

12. Automated logging mechanism

13. Logger structure Outer JAR Inner JAR Contain more than one inner JARs
Handle authentication of entities to access the data
Selecting the correct inner JAR
Checking the JVM’s validity
Managing the Graphical User interface
Inner JAR
Encrypted data, retrieval of log files, display enclosed data
Two options
Pure log
Access log

14. Log record generation The log records(Lr) are generated as
Lr = r1, r2, r3, r4... Rk
rk = ( id, action, T, loc, h((id, action, T, loc)ri-1…r1), sig )
rk = log record
id = user identification
action = perform on user's data
T = Time at location loc
loc = Location
h((id, action, T, loc)ri-1…r1) = checksum component
sig = Signature of record by server
Checksum is computed using hash function,
H[i] = f(H[i − 1] ,m[i])

15. Ensuring log correctness
Verify the access time, locations & actions
JAR can perform an IP lookup to find the location of the cloud service provider
Actions to user’s data has to be logged
Mainly four types of actions used:
View
Download
Timed access
Location-based access.

16. Dependabililty of logs
JARs Availability
Log harmonizer deals with
Copies of JARs and logger components
Recovering of corrupted logs
Stores error correction information
Decrypt the log records & handle duplicate records
Log Correctness
JRE of the system must remain unmodified
Verify the integrity of the logger component by:
Repair the JRE before logger is launched
Insert hash codes to detect modifications of the JRE

17. End-to-end auditing mechanism
Push and Pull Mode
Push mode:
The logs are periodically pushed to the data owner by the harmonizer:
Ensures size of the log files does not explode
Enables timely detection and correction of any loss or damage to log files
Pull mode
auditors may retrieve the logs anytime
Pull message contains FTP pull command

18. End-to-end auditing mechanism
Algorithms:
Pushing strategy
Pull strategy
Hybrid strategy

19. Security discussion The attacker copies entire JAR files.
Copying Attack
The attacker copies entire JAR files.
Disassembling Attack
Disassemble the JAR file & attempt to extract useful information
Man-in-the-Middle Attack
Attacker intercept messages during authentication of service provider with certificate authority, and reply messages
Compromised JVM Attack
Attacker try to compromise the JVM

20. Performance study Experimental Settings
By setting up a small cloud, using the Emulab testbed
On OpenSSL-enabled servers
Servers are installed with Eucalyptus
Used Linux-based servers running Fedora 10 OS
a 64-bit Intel Quad Core Xeon E5530 processor
4 GB RAM
500 GB Hard Drive

21. Performance study
Experimental Results
Log Creation Time

22. Performance study Authentication Time Time Taken to Perform Logging
Not too much overhead is added
Performance can be further improved by caching the certificates
Time Taken to Perform Logging
Time for executing the action is negligible

23. Performance study
Log Merging Time

24. Performance study
Size of the Data JAR Files

25. Conclusion CIA performs automatic authentication of users
Data owner can confirm that his data is safe in the cloud by using auditing mechanism
Able to distribute applications to many different mobile devices
Information gathering capabilities is high
High portability

26. References
[1] Smitha Sundareswaran, Anna C. Squicciarini and Dan Lin, "Ensuring Distributed Accountability for Data Sharing in the Cloud,", IEEE Transaction on dependable a secure computing, VOL. 9, NO. 4, pg , 2012.
[2] S. Pearson and A. Charlesworth, "Accountability as a Way Forward for Privacy Protection in the Cloud, " Proc First Int'l conf. Cloud Computing, 2009.
[3] B. Chun and A. C. Bavier ,"Decentralized Trust Management and Accountability in Federated System," Proc. Ann. Hawaii Int'l Conf. System Science (HICSS), 2004.
[4] B. Crispo and G. Ruffo, “Reasoning about Accountability within Delegation,” Proc. Third Int’l Conf. Information and Comm. Security (ICICS), pp , 2001 26

27. Thank you! 