1. Computer System Design Lab 1 Inverted Index Based Multi-Keyword Public-key Searchable Encryption with Strong Privacy Guarantee Bing Wang * Wei Song *† Wenjing Lou * Y. Thomas Hou * * Virginia Polytechnic Institute and State University, Blacksburg, VA, USA † Wuhan University, Wuhan, Hubei, China

2. Computer System Design Lab 2 Motivation

3. Computer System Design Lab 3 Motivation Previous Inverted index work Curtmola et al Limitations (1) the keyword privacy is compromised once a keyword is searched. (2) existing inverted index based search- able schemes do not support conjunctive multi-keyword search

4. Computer System Design Lab 4 Our work Propose a practical inverted index based public- key searchable encryption scheme. Design a probabilistic trapdoor generation algorithm to break the trapdoor linkability.

5. Computer System Design Lab 5 Inverted Index Note: Suppose we want to search the texts "i love you," "god is love," "love is blind," and "blind justice.” If we index by (text, character within the text), the index with location in text is: blind (3,8);(4,0) god (2,0) i (1,0) is (2,4);(3,5) justice (4,6) love (1,2);(2,7);(3,0) you (1,7)

6. Computer System Design Lab 6 System model

7. Computer System Design Lab 7 Scheme Details Setup IndexGen TrapdoorGen Query

8. Computer System Design Lab 8 Setup The data owner first chooses two k-bit prime numbers p, q. Then the data owner follows the key generation process to generate the key pair for the Paillier algorithm and publishes the public key(pk) to the cloud server..

9. Computer System Design Lab 9 IndexGen 1)Each keyword w i has its corresponding inverted list I wi 2) The data owner encrypts the coefficients of each polynomial. 3)Data owner constructs a dictionary matrix M D based on the tag of keywords. Outsource to cloud sever

10. Computer System Design Lab 10 TrapdoorGen 1)The data owner first generates a polynomial for the entire dictionary P D 2)When the data owner receive a query request Q from user and then constructs a P Q (x)

11. Computer System Design Lab 11 Query After receiving the trapdoor, the cloud server first calculates V. Then all the values are organized as a vector: After that, the cloud server calculates P R(x) and returns it back to the user.

12. Computer System Design Lab 12 SIMULATION Environment Setting Python to implement Windows 8.1 PC with Intel Core i3 and 4 Gigabyte memory. Dataset Part of the Enron dataset

13. Computer System Design Lab 13 SIMULATION

14. Computer System Design Lab 14 SIMULATION

15. Computer System Design Lab 15 SIMULATION

16. Computer System Design Lab 16 Conclusion Proposed a novel construction of a public- key searchable encryption scheme based on inverted index. Our probabilistic trapdoor generation algorithm prevents the cloud server from linking the trapdoors. Supports multi-keywords conjunctive search.

17. Computer System Design Lab 17 Thanks!