Public key authenticated encryption with field-free subset conjunctive and disjunctive keyword search against keyword guessing attacks

Public Key Encryption with Keyword Search ( PEKS) is a promising cryptographic primitive that allows searching over encrypted data in secure data outsourcing services. Initially, several PEKS schemes were developed for conjunctive keyword search, but they relied on certain assumptions regarding keyword fields. To address this limitation, an Efficient Public-Key Encryption with Field-free Conjunctive Keyword Search (PEFCK) scheme was introduced in 2015. PEFCK enables conjunctive keyword search without any specific ordering of the keywords. However, PEFCK is vulnerable to keyword guessing attacks (KGA), which compromise its security. To overcome the KGA vulnerability, we propose a new scheme called Public Key Authenticated Encryption with Field-free Subset Conjunctive and Disjunctive Keyword Search (PAEFSCDKS), which leverages the mathematical concept of Lagrange Polynomials. This scheme incorporates three key features: 1) Sender Authentication: The sender encrypts the keywords using both the receiver's public key and its private key, ensuring sender authenticity and integrity. 2) Secure Channel-free: Unlike traditional approaches, our scheme does not require a secure channel to transfer data from the receiver to the cloud server. This eliminates the need for additional secure communication overhead. 3) Subset Conjunctive and Disjunctive Keyword Search: The receiver can perform queries that involve both subset conjunctive and disjunctive keywords, enabling more flexible and powerful searches. Furthermore, we demonstrate that our proposed scheme achieves provable security under index indistinguishability and trapdoor indistinguishability against both internal and external adversaries. Finally, through performance analysis, we show that our proposed scheme outperforms similar PEKS schemes in terms of both theoretical and experimental evaluations.