A Pairing-Free Data-Sharing Scheme Based on Certificateless Conditional Broadcast Proxy Re-Encryption Suitable for Cloud-Assisted IoT

In Cloud-Assisted IoT (CAIoT), the large amounts of data generated by devices and sensors need to be shared and stored efficiently and securely. Broadcast proxy re-encryption (BPRE) technology ensures data privacy and enables efficient sharing. A significant issue with existing BPRE schemes is that the re-encryption permissions of the cloud server are uncontrolled, potentially leading to re-encryption operations without the consent of the data owner, and increasing the risk of data leakage. Additionally, most conditional proxy re-encryption (CPRE) schemes rely on computationally intensive bilinear pairing operations, making them unsuitable for resource-constrained IoT devices. To address this, this paper proposes a new certificateless conditional broadcast proxy re-encryption scheme, where the data owner sets conversion conditions when generating the original ciphertext and re-encryption keys, ensuring that only ciphertext meeting the conditions can being converted, thus preventing the cloud platform from abusing re-encryption permissions. Security analysis shows that the proposed scheme can resist chosen ciphertext attacks and collusion attacks in the random oracle model. Performance evaluation shows that the proposed scheme avoids bilinear pairing and hash-to-point operations, reducing the computational cost for the data owner. This improves computational efficiency, making it more suitable for CAIoT scenarios.