Cryptology ePrint Archive: Report 2020/1211

Public-key Authenticate Encryption with Keyword Search Revised:\\ Probabilistic TrapGen algorithm

Leixiao Cheng and Fei Meng

Abstract: Public key encryption with keyword search (PEKS) is first introduced by Boneh et al. enabling a cloud server to search on encrypted data without leaking any information of the keyword. In almost all PEKS schemes, the privacy of trapdoor is vulnerable to inside keyword guessing attacks (KGA), i.e., the server can generate the ciphertext by its own and then run the test algorithm to guess the keyword contained in the trapdoor. To sole this problem, Huang et al. proposed the public-key authenticated encryption with keyword search (PAEKS) achieving trapdoor privacy (TP) security, in which data sender not only encrypts the keyword but also authenticates it by using his/her secret key. Qin et al. introduced the notion of multi-ciphertext indistinguishability (MCI) security to capture outside chosen multi-ciphertext attacks, in which the adversary needs to distinguish two tuples of ciphertexts corresponding with two sets of keywords. They analysed that Huang's work cannot achieve MCI security, so they proposed an improved scheme to match both the MCI security and trapdoor privacy (TP) security. In addition, they also defined the notion of multi-trapdoor privacy (MTP) security, which requires to distinguish two tuples of trapdoors corresponding with two sets of keywords.

Unfortunately, trapdoor generation algorithms of all above works are deterministic, which means they are unable to capture the security requirement of MTP. How to achieve MTP security against inside multi-keyword guessing attacks,i.e., designing a probabilistic trapdoor generation algorithm, is still an open problem.

In this paper, we solve this problem. We initially propose two public-key authenticated encryption with keyword search schemes achieving both MCI security and MTP security simultaneously. We provide formal proof of our schemes in the random oracle model.

Category / Keywords: public-key cryptography / Public key encryption; Keyword search; Keyword guessing attacks; Multi-ciphertext indistinguishability; Multi-trapdoor privacy

Date: received 2 Oct 2020, last revised 12 Apr 2021

Contact author: mengfei_sdu at 163 com

Available format(s): PDF | BibTeX Citation

Version: 20210412:135234 (All versions of this report)

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