Searchable Attribute-Based Proxy Re-encryption: Keyword Privacy, Verifiable Expressive Search, and Outsourced Decryption

In this paper, we address the open problem posed by Ge et al. in 2020, which was to design a new attribute-based proxy re-encryption with keyword search scheme (ABPRE-KS) for enabling more expressive keyword search. ABPRE-KS exhibits promising potential in facilitating data searching and sharing through the implementation of one-to-many access control mechanism. However, existing ABPRE-KS schemes support single keyword search framework resulting in low search efficiency and poor user search experience. Also, maintaining keyword privacy, and protecting the outsourced ciphertexts and tokens from keyword guessing attacks (KGAs) quite challenging in ABPRE-KS framework. To overcome these issues, we propose an attribute-based proxy re-encryption scheme with Boolean keyword search (ABPRE-BKS) in the large attribute universe framework. Our scheme not only offers an efficient Boolean keyword search framework but also it enables constant decryption cost on the data user’s side. The data user needs to perform only constant number of computations to recover both the original and the re-encrypted ciphertext. We define ABPRE-BKS and its security models. And, we prove that our scheme achieves ciphertext indistinguishability against adaptive chosen ciphertext attack, ciphertext and token indistinguishability against chosen keyword attack, and non-interactive verifiability. The efficiency of our proposed construction is demonstrated through a comparison of its functionalities and performance with the existing such schemes.