Expressive Public-Key Encryption With Keyword Search: Generic Construction From KP-ABE and an Efficient Scheme Over Prime-Order Groups

Public key encryption with keyword search (PEKS) allows a cloud server to retrieve particular ciphertexts without leaking the contents of the searched ciphertexts. This kind of cryptographic primitive gives users a special way to retrieve the encrypted documents they need while preserving privacy. Nevertheless, most existing PEKS schemes only offer single-keyword search or conjunctive-keyword search. The poorly expressive ability and constantly inaccurate search results make them hard to meet users’ requirements. Although several expressive PEKS (EPEKS) schemes were proposed, they entail high computation and communication costs. An ideal EPEKS scheme should enable fast and accurate ciphertext retrieval, while lowering the storage server’s load and reducing the amount of communication data. Drawing on the strongly expressive ability of key-policy attribute-based encryption (KP-ABE), we propose a generic construction of EPEKS from KP-ABE. We demonstrate that the derived EPEKS scheme is secure under the chosen keyword attack if the implicit KP-ABE scheme fulfills the anonymity under the chosen plaintext attack. Furthermore, we present a concrete EPEKS scheme over the prime-order groups. The comparison and experimental results indicate that our scheme is more efficient than the existing EPEKS schemes.