Implementation of access control in cloud storage system is the essential method to protect users' data from revealing sensitive information. The paper mainly investigates key technologies of access control in cloud storage system, including intra cloud and among multi-clouds. Firstly, we discuss about the focuses in recent researches and challenges of access control in cloud storage system. The access control researches here refer to cipher-text and cross-domain access control in cloud storage

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... system. The key technologies introduce Ciphertext-Policy Attribute-Based Encryption algorithm(CP-ABE), ontology based attributes mapping, algebra based policies integration, solutions for identification, access authorization and identity federation. And the status of these fields is described next. At last, we concluded this paper and proposed some directions in the future work of access control research in cloud storage system. This paper can help to understand the key technologies of access control in cloud storage and helpful in the future researches.