# Multi-Authority Revocable Access Control Method Based on CP-ABE in NDN
## 2 Related Works  
The information caching technology in NDN simplifies the request and distribution of content, which is beneficial to solve the problem of efficient access and secure transmission of data in cloud computing. The information cache decouples the publisher from the data, causing the publisher to lose control of the content and the risk of data leakage. Therefore, access control is especially important for NDN security. In order to protect data privacy and realize effective access control, [PERSON] first proposed identity-based encryption in 1984 [8]. On this basis, [PERSON] and [PERSON] first proposed fuzzy identity encryption, also known as attribute encryption [9]. After that, [PERSON] et al. [10] and [PERSON] et al. [11] constructed two more practical attribute encryption schemes, namely Key-Policy Attribute-based Encryption (KP-ABE) and Ciphertext-Policy Attribute-based Encryption (CP-ABE). In the original attribute encryption scheme, only a single central authority manages all attributes. In real life, it is not practical to issue a key for all attributes of a user, the authority has a heavy workload and requires complete credibility, and a single authorization failure can cause a system crash. For the purpose of solving the above problems, the attribute encryption schemes of multiple multi-attribute authorities are proposed in the subsequent research. The idea of managing different attributes of users by multiple attribute authority (AA) is first proposed by [PERSON] et al. in [12]. Managing multiple attributes by multiple attribute authorities can alleviate the workload of a single authority, while avoiding system crashes that can result from a single authorization failure. CP-ABE is considered to be one of the most fitness technologies for data access control in cloud storage. At present, CP-ABE is divided into single-privilege CP-ABE and multi-privilege CP-ABE program [13]. [PERSON] et al. [14] proposed another CP-ABE scheme with fine-grained attribute revocation. They re-encrypt the ciphertext using the attribute group key. However, their method is not effective in resisting collusion attacks, and may even fail to resist. [PERSON] et al. [15; 16] proposed two CP-ABE schemes for multi-authorization centers that support decryption outsourcing, enabling effective cloud data sharing and user revocation. [PERSON] et al. [17] proposed a smart city cloud data agent auxiliary access control scheme to realize access control and user revocation of smart city cloud data. Both NDN information caching and cloud storage have problems with the decoupling of content and content owners. In order to realize secure and efficient access control of NDN cache content, attribute-based access control in NDN has attracted more and more researchers' attention. Single authorization: [PERSON] et al. designed a CP-ABE-based naming scheme [18] that increases the naming overhead and does not consider the issue of consumer revoke. In terms of content caching, [PERSON] et al. proposed an instant-revokable NDN access control mechanism, which solves the user-level revocation problem, but does not consider the attribute-level revocation and key leakage problems. The proxy server performs user authentication online at all times, and no specific formalization algorithm and security analysis and certification are given in the text. Multi-authorization: [PERSON] et al. proposed a novel NDN access control scheme to solve this problem [19]. The system is based on CP-ABE multi-authorization, revocable access control scheme. The solution implements an indirect revocation of consumer users. In addition, the program did not use experiments to prove the time of content release and content request. However, as far as the NDN system is concerned, attribute revocation and users have been its challenging problems. There are many reasons why attribute revocation and users will cause challenges in the NDN system, such as the following reasons.