On Security of a Secure Channel Free Public Key Encryption with Conjunctive Field Keyword Search Scheme

Public key encryption with keyword search is a practical cryptographic paradigm that enables one to search the encrypted keyword without compromising the security of the original data. Recently, Hwang et al . proposed a secure channel free public key encryption with conjunctive field keyword search (SCF-PECKS) scheme and claimed that their scheme can withstand the keyword guessing attack and does not require the secure channel. In this paper, by presenting three concrete attacks, we demonstrate that Hwang et al .’s SCF-PECKS scheme fails to achieve security against keyword guessing attacks by either the outsider attackers or the malicious insider servers. The presented attacks show that Hwang et al .’s SCF-PECKS scheme is vulnerable to the keyword guessing attack regardless whether the trapdoor is sent in public or secure channel. Therefore, devising a secure SCF-PECKS scheme remains an unsolved problem until now. DOI: http://dx.doi.org/10.5755/j01.itc.47.1.16137