###### Abstract  
This study presents a decentralised ciphertext-policy attribute-based encryption (CP-ABE) scheme designed for secure and efficient access control in resource-constrained Internet-of-Things (IoT) environments. By utilising multi-authority architecture and outsourced computation, the scheme enhances scalability, simplifies key management by eliminating reliance on a certificate authority (CA), and ensures data confidentiality through randomised proxy keys. It is particularly suited for multi-scenario IoT applications involving information sharing, such as smart cities or industrial automation in strategic alliances or conglomerates. Demonstrating security against chosen-plaintext attacks under the decisional bilinear Diffie-Hellman assumption, the scheme offers a practical and scalable solution for decentralised access control. decentralised access control; secure access; multi-authority ABE; outsourcing; multi-scenario IoT 2020 IEEEexample:BSTcontrol  
using data encryption is essential. Encryption methods can be categorised into symmetric encryption and asymmetric cryptography [11]. Symmetric encryption is faster and requires fewer resources but uses the same key for encryption and decryption, creating security risks [12]. Key transmission keys between devices is challenging, and managing a large number of keys is cumbersome. Asymmetric encryption, which employs a public key for encryption and a private key for decryption, solves the key distribution issue. However, in IoT's one-to-many and many-to-many communication scenarios, key management remains complex. When a data user wants to decrypt the data, the encryption method must consider whether the user's attributes comply with the access policy. As a solution, [PERSON] et al. [13] proposed a new encryption method called attributed-based encryption (ABE), which is an asymmetric encryption mechanism where the key and ciphertext are dependent on attributes that conform to the access policy and decrypt the ciphertext. Unlike traditional encryption methods, ABE is a one-to-many encryption mechanism, making it suitable for IoT environments by facilitating fine-grained access control and simplifying key management. ABE is divided into two types: key-policy attribute-based encryption (KP-ABE) [13] and ciphertext-policy attribute-based encryption (CP-ABE) [14]. Among these, CP-ABE assigns attributes to the private key for data users. The data owner defines the access policy and attaches it to the ciphertext. The ciphertext can be correctly decrypted if the data user holds the attribute key that satisfies the access policy. Conversely, if an attacker does not possess the private attribute key that satisfies the access policy, they cannot decrypt the ciphertext. This fine-grained access control mechanism ensures that only authorised users with required attributes can access data, making CP-ABE suitable for secure data sharing in dynamic environments. Furthermore, fine-grained access control provides precise control over data sharing [15], enabling secure information exchange across various sectors, such as healthcare, finance, and smart cities, without exposing sensitive information. This mechanism enhances multi-party collaboration security, ensuring that different entities can interact with mutual trust while maintaining data confidentiality. When CP-ABE is combined with the IoT, it faces the issue of limited resources [16; 17]. IoT devices are often limited in computing power, storage space, and energy resources, and the number of IoT devices on the network and application can be vast. As such, the access tree construction for the access policy can become complicated, and the number of attributes will become large. The encryption and decryption time of CP-ABE is linearly positively correlated to the size of the key, the number of attributes, and access tree complexity. It is difficult for IoT devices to bear the burden of complex calculations and access space. Therefore, subsequent scholars have studied the lightweight CP-ABE [18; 19] suitable for IoT.