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Efficient Conjunctive Keyword Search on Encrypted Data Storage System. Author : Jin Wook Byun Dong Hoon Lee Jongin Lim. Presentered by Chia Jui Hsu Date : 2008-08-05. Outline. Introduction Related Works Example Contribution Security Definition
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Efficient Conjunctive Keyword Search on Encrypted Data Storage System Author:Jin Wook Byun Dong Hoon Lee Jongin Lim Presentered by Chia Jui Hsu Date:2008-08-05
Outline • Introduction • Related Works • Example • Contribution • Security Definition • Formal Security Proof • Conclusion • References
Introduction • Encryption of sensitive data • Management of encryption/decryption keys. • But, it makes data be random and unreadable to anyone other than the users holding the encrypted keys.
Related Works (1/3) • Web-based personal storage systems • Two entities are involved • Data supplier uploads encrypted data, then searches data containing keywords • Song et al. [13] • In 2000, they first suggest efficient and provably secure keyword search scheme by block cipher • Goh[8] • Goh suggested a secure search scheme using a Bloom filter • Chang and Mitzenmacher[6] • They suggested a practical keyword search protocol in terms of communication and storage overheads.
Related Works (2/3) • Conjunctive keyword search • Golle et al.’s work [7] • They suggested two conjunctive keyword search protocols enabling users to search conjunctively. • Golle I • Communication and storage costs • It requires O(n) • Golle II • Unverifiable computational assumption • Is it really secure ?
m fields From To Date Status D1 D2 n docs Dn Related Works (3/3) • We assume structured documents where keywords are organized by fields The documents are the rows of the matrix Di = (Wi, 1, …, Wi, m)
√ X Example From To Status • Capability for emails from Alice to Bob is • Let s = fk (alice) + fk (Bob) Problem: the size of capabilities is linear in n
Contribution • Comparison Table • Efficiency + Provable Security • ECKS-PS : Efficient Conjunctive Keyword Search in the Personal Storage Systems
Security Definition (1/3) • Database • n row and m column
Security Definition (2/3) • Conjunctive Keyword Search
Security Definition (3/3) • SS-CTA security in the PS setting
Formal Security Proof • Multi decisional bilinear Diffie-Hellman (MDBDH) = DBDH • Reducing the security to the assumption of MDBDH • DBDH problem • DBDH assumption • If no polynomial algorithm has non-negligible advantage e in solving DBDH problem
Conclusion • Analysis of Some Keyword Search Schemes in Encrypted Data, 2008 • IK Rae Jeong and Jeong Ok Kwon • Conjunctive Keyword Search scheme do not provide semantic security.
References • Efficient Conjunctive Keyword Search on Encrypted Data Storage System, 2006 • http://jwbyun.ptu.ac.kr/[EuroPKI2006]final.pdf • Analysis of Some Keyword Search Schemes in Encrypted Data, 2008