Controllable encrypted data sharing scheme with key update for blockchain-assisted IoT

Blockchain is utilized as a multi-party collaboration platform on the Internet of Things (IoT) for distributed data sharing. Considering the privacy concerns raised by blockchain, privacy-preserving data sharing is increasingly required, and proxy re-encryption (PRE) is a significant method to address the data privacy problem. However, it remains challenging to achieve controllable user authorization in transaction data sharing, as well as key update to ensure forward security without third-party assistance. To address these issues, we design a puncturable autonomous path proxy re-encryption (Pun-AP-PRE) scheme that combines autonomous path proxy re-encryption (AP-PRE) with puncturable encryption to support the controlled delegation path, while the secret key can be punctured to revoke its ability to decrypt specific messages. Then, using the designed Pun-AP-PRE, we construct a secure sharing solution for encrypted data on the blockchain. It allows data owners to control the priority of user access to the data for controllable authorization. Further, the data owners and users can self-update their decryption keys to guarantee forward security. Rigorous security analysis shows that our proposed scheme is secure against the chosen-plaintext and collusion attacks. The comprehensive performance evaluation illustrates that the efficiency and practicality of our scheme.