OD‐H‐SABE: A Hierarchical Searchable Attribute‐Based Encryption Scheme With Outsourced Decryption for Blockchain‐Based Data Sharing

ABSTRACT The growing demand for data sharing in domains such as health care highlights limitations in existing solutions, including low search efficiency, coarse‐grained access control, and heavy decryption overhead on users. To address these challenges, this paper proposes a hierarchical searchable attribute‐based encryption scheme with outsourced decryption for blockchain‐based data sharing (OD‐H‐SABE). OD‐H‐SABE introduces a hierarchical attribute structure alongside an outsourced decryption mechanism that offloads computationally intensive bilinear operations to the cloud server. Consequently, users only need to perform a single lightweight operation to complete decryption, significantly alleviating the computational burden. Furthermore, the scheme integrates searchable encryption with multi‐keyword aggregate hashing, enabling efficient search with constant complexity regardless of the number of keywords. Leveraging the transparency and immutability of blockchain, smart contracts verify the integrity of results returned from the cloud server, ensuring data security and trustworthiness throughout the sharing process. Theoretical and experimental analyses demonstrate that OD‐H‐SABE achieves notable advantages over traditional schemes in terms of security, search efficiency, and computational overhead. For example, compared to MKS‐VABE and BEM‐ABSE, OD‐H‐SABE reduces encryption and user‐side decryption overhead by approximately 20% and 42%, respectively. This makes it a practical and lightweight solution for constructing secure and efficient blockchain‐based data‐sharing platforms.