Efficient data encryption, updating and access control method for cloud storage

The invention discloses an efficient data encryption, updating and access control method for cloud storage, which belongs to the technical field of network information safety and computer software. The method can realize quick block encryption replacement for plaintext data, so that data confidentiality is guaranteed while abuse of user data by a cloud server can be prevented. The method can realize efficient updating for ciphertext data without re-encrypting and uploading a whole data file, so that system transmission and storage efficiency is improved. The method can realize dual permission control for the data file, ciphertext access rights are formulated by data owners but executed by the cloud server, and secret key materials for decrypting ciphertexts are controlled by the data owners, so that data file control is enhanced, and permission revocation can be flexibly realized. Encryption of the plaintext data and processing of the ciphertext data can be realized by the method at low cost, duel replacement for the plaintext data enables a data applicant to obtain completely different ciphertext results in each time of application and prevents the cloud server from abusing the user data, accordingly data confidentiality is further enhanced, and the method has bright application prospect in data cloud storage.