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 (DO), 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 Internet of Things (IoT) devices. To address this, this article proposes a new certificateless conditional BPRE scheme, where the DO 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 attack 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 DO. This improves computational efficiency, making it more suitable for CAIoT scenarios.