Revocable Blockchain-Aided Attribute-Based Encryption With Escrow-Free in Cloud Storage

The massive amount of data generated by the Internet of Things (IoT) and the need to store that data presents a huge challenge for storage. However, meeting this challenge has also driven the development of storage technologies, especially those related to cloud storage. Although attribute-based encryption (ABE) schemes are commonly used to achieve data confidentiality and fine-grained access control in cloud storage, there is still an inherent problem with ABE schemes, namely the key escrow problem. In this paper, we propose a revocable blockchain-aided ABE with escrow-free (BC-ABE-EF) system that resolves the key escrow problem by replacing the traditional key authority with a consortium blockchain. The keys are generated between the blockchain and the data user through a secure key issuing protocol, and the blockchain cannot obtain the user's full key alone. Furthermore, utilize the decryption cloud server to schedule pre-decryption operations in cloud and introduce a group manager to update the group keys of unrecovered users and generate re-encryption keys. The security analysis shows that our scheme is secure under the Decisional Computation Diffie Hellman (DCDH) assumption. The effectiveness of the scheme is demonstrated by simulating the BC-ABE-EF scheme and comparing it based on performance analysis.