A Secure Key-Aggregate Keyword Retrieval Scheme Over Encrypted Data in Cloud Computing

Abstract

Key-aggregate retrieval enables a cloud server, on behalf of delegated users, to perform keyword searches over data encrypted under multiple public keys. While existing key-aggregate searchable encryption schemes provide efficient data sharing, many of them remain vulnerable to keyword guessing attacks, leading to potential leakage of keyword ciphertexts and search trapdoors. Such vulnerabilities significantly undermine data privacy in cloud-based applications, particularly in emerging environments such as the Internet of Things (IoT). In this paper, we propose a secure and efficient key-aggregate keyword retrieval scheme for encrypted data in cloud computing. The proposed scheme allows a data owner to selectively share encrypted documents with multiple users using a single compact aggregate key, while enabling authorized users to delegate keyword search capabilities to the cloud server without revealing sensitive keyword information. To address privacy concerns, the scheme is designed to prevent keyword guessing attacks and ensure confidentiality of both keyword ciphertexts and trapdoors. We formally define the security model of the proposed scheme and prove its security under the indistinguishable selective-file chosen keyword attack (IND-SF-CKA) model. Performance analysis and experimental simulations demonstrate that the proposed approach achieves strong security guarantees with low computation and communication overhead, making it practical for cloud-assisted IoT and large-scale encrypted data sharing applications.