1. Privacy Preserving Cloud Data Access With Multi-Authorities Taeho Jung 1, Xiang-Yang Li 1, Zhiguo Wan 2, Meng Wan 3 Illinois Institute of Technology, Chicago 1 Tsinghua University, Beijing 2 Ministry of Education, Beijing 3

3. Image credit EFF website (https://www.eff.org/), StorageNewsletter ( http://www.storagenewsletter.com )https://www.eff.org/ http://www.storagenewsletter.com

4. Say No ! We want privacy !

5. Our concerns in clouds  Data privacy  Data manipulation (delete, create etc) privilege is not properly managed  User profile privacy  User information is disclosed for access control

6. Existing Encryptions  Public key encryption  Identity based encryption  Attribute based encryption Professor OR Ph.D University: IIT Position: Ph.D

7. Attribute Based Encryption (ABE) 2/2 1/3 Ciphertext Professor Ph.D Master I.I.T C.S Department University: Illinois Institute of Technology, Major: Computer Science, Position: Professor University: Illinois Institute of Technology, Major: Computer Science, Position: Professor Secret-Sharing 7 Access Tree ANDOR

8. Attribute Based Encryption (ABE) Data PublisherData Consumer Request key Attribute Authority If I am compromised, the whole system die! Will authority know who I am? File Server upload download

9. Similar Approaches  Chase et al. [TCC’05, CCS’09] Multi-authority ABE  Key-Policy  Overlap-based Matching  Lewko et al. [EUROCRYPT’11] Multi-authority CP-ABE  LSSS-matrix based, conversion from Boolean formula only

10. Our Approach  AnonyControl  Make the attribute authority (key generator) distributed.  Generalize access control to privilege control  Privilege to read, delete, create, modify, etc.  We DON’T implement computable encryption!  Contributions  Each authority knows only part of users’ identity  One authority being compromised does not break the system  Being able to control the data manipulation  Implemented a prototype system

11. Overview of AnonyControl  Core Algorithms Design  Setup  KeyGenerate  Encrypt  Decrypt

12. Algorithm - Setup AA1 AA2 AA3 AA4 Uniform Public Key Joint computation Master Key 1 (secret) Master Key 2 (secret) Master Key 4 (secret) Master Key 3 (secret) Bilinear mapping Next talk

13. Algorithm - Setup AA1 AA2 AA3 AA4

14. Algorithm - Setup AA1 AA2 AA3 AA4

15. Algorithm - KeyGenerate AA1 AA2 AA3 AA4 User’s secret key Joint computation

16. Algorithm - Encrypt ……

17. Algorithm - Decrypt …… Data consumer uses his secret key to recover secret values at each tree’s root node. (secret-sharing)

18. Concerns solved?

19. Further concerns?

20. Prototype System

21. Execution Time for Core Algorithms 21

22. Conclusion Semi-anonymous – only partial attributes are disclosed to single authority Privilege control Tolerate up to N-2 compromise attack 22

23. 23 www.iit.edu/~tjung www.cs.iit.edu/~winet/index.html