Abstract: In order to protect the confidentiality of user data and user privacy in cloud storage system,multiple permissions secure access control scheme combining ciphertext-policy attribute-based encryption(CP-ABE) and XACML was proposed.The confidentiality of user data is ensured by CP-ABE encryption and properties of fine-grained access control are implemented by XACML framework.In cloud storage system user data is encrypted by symmetric encryption mecha-nism,and symmetric key encryption uses the CP-ABE.Simulation results show that the model is efficient,flexible,and secure.Security analysis shows that the scheme can resist collusion attacks,has data confidentiality and backward forward confidentiality.

Key words: Cloud storage,Access control,Ciphertext-policy attribute-based encryption,XACML