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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

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Motivation

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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

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Our work• Propose a practical inverted index based

public- key searchable encryption scheme.

• Design a probabilistic trapdoor generation algorithm to break the trapdoor linkability.

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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)

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System model

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Scheme Details • Setup• IndexGen• TrapdoorGen• Query

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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.

.

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IndexGen

1) Each keyword wi has its corresponding inverted list Iwi

2) The data owner encrypts the coefficients of each polynomial.

3) Data owner constructs a dictionary matrix MD based on the tag of keywords.

Outsource to cloud sever

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TrapdoorGen

1) The data owner first generates a polynomial for the entire dictionary PD

2) When the data owner receive a query request Q from user and then constructs a PQ(x)

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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 PR(x)

and returns it back to the user.

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SIMULATION • Environment Setting

Python to implement Windows 8.1 PC with Intel Core i3 and

4 Gigabyte memory. • Dataset

Part of the Enron dataset

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SIMULATION

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SIMULATION

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SIMULATION

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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.

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Thanks!