## 2 Related Works  
In IoT applications, where security and access control are critical, attribute-based encryption (ABE) schemes offer an effective solution for protecting sensitive data [20]. IoT environments often consist of interconnected devices with limited computational and storage capabilities, making traditional key management approaches inefficient and susceptible to security risks. ABE schemes provide fine-grained access control and a one-to-many key management mechanism. These features ensure that only authorised entities can access specific data, thereby enhancing security while minimising the overhead associated with key distribution and updates, which is particularly advantageous in dynamic IoT ecosystems. Both KP-ABE and CP-ABE utilise an access tree, making them suitable for multi-device environments. In cloud-based scenarios, these schemes enable users to encrypt and decrypt data based on authorised attributes, effectively addressing the challenges of managing keys for multiple users [21; 22; 23]. When integrating IoT applications, such as smart cities, industrial automation, and healthcare for cross-domain collaboration, ABE schemes provide a robust and scalable framework for secure and efficient data sharing [15]. These schemes enable fine-grained access control, ensuring that only authorised users with the appropriate attributes can access sensitive information, thereby enhancing data security and privacy. Furthermore, by ensuring data confidentiality and access control even for resource-constrained devices [16; 17], ABE effectively addresses critical security challenges in IoT systems. This makes ABE particularly well suited for dynamic and distributed environments, where multiple entities must securely exchange and process data while preserving system integrity and trustworthiness. In contexts where IoT systems integrate with cloud computing, the decryption of multi-attribute ciphertext using CP-ABE can be computationally demanding, owing to the limited resources of many terminal devices [24]. Research suggests that utilising external computing resources can help reduce the computational burden on these resource-constrained devices. This approach is often implemented through proxy re-encryption schemes [25], which enable partial decryption by an external entity, thereby reducing the computational workload on terminal devices while maintaining data security. In IoT architectures, cloud-based infrastructure is frequently utilised to assist with computations, reducing processing loads through techniques such as elliptic curve cryptography, bilinear mapping, and identity authentication. [PERSON] et al. [18] emphasises the importance of ensuring that the CA does not generate proxy keys during outsourced encryption and decryption operations. This precaution mitigates privacy concerns and reduces the risks of proxy key leakage and misuse. To further address these issues, re searchers [17] have proposed generating proxy keys to facilitate the partial decryption process, leaving users responsible for the final stage of decryption. The reliance on a trusted third party, typically a CA, is a fundamental feature of ABE systems. The CA plays a crucial role in generating public parameters, public and private keys, and verifying user authenticity. However, managing updates to attribute keys imposes a significant burden on the CA [26], especially in systems with numerous end devices. To address this limitation and improve key management efficiency [27], multi-authority access control mechanisms have emerged as a promising solution. These mechanisms [23; 26; 28; 29; 30; 31; 32] distribute computational responsibilities among multiple authorities, ensuring the independent verification of data accuracy and integrity. By implementing a multi-authority framework, the CA is better equipped to manage updates to attribute keys and revocations, streamlining the process without disrupting users or compromising the security of encrypted data.