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Proxy re-encryption allows a proxy to convert a ciphertext related to a certain access policy into another one with a different access policy without uncovering the underlying plaintext, which makes the proxy re-encryption technology to be an important technology for data sharing between users.However, the proxy re-encryption schemes are mostly based on single authority, which have some problems such as single power and performance bottleneck of the authority organization and high computing burden on user’s client.At the same time, most schemes do not have the five basic characteristics of proxy re-encryption: one-way encryption, non-interaction, repeatability, controllability and verifiability.In order to solve these problems, a CP-ABE proxy re-encryption scheme for cloud computing based on multi-authority with repeatability and controllability was proposed.Based on the ciphertext policy attribute encryption scheme, proxy servers of encryption and decryption were introduced to reduce the computing burden on the user’s client, and multi-attribute authorization were set to disperse the authority of the central authority.The proxy re-encryption was improved from multiple aspects.Random factors and ciphertext sub-item set in the re-encryption key can realize one-way encryption and controllability.The re-encryption key was independently generated by the client without the participation of servers, which can support users to share data when the data owner is not online.Encrypting the ciphertext sub-item set in the initial ciphertext many times can achieve repeatability.The verification sub-item set in the initial ciphertext allowed the user to verify whether the outsourcing and re-encryption results were correct.Compared with other schemes, the user’s client computing overhead of the proposed scheme was small, and the user can decrypt the original ciphertext only by performing constant times of exponential operation.Based on q-parallel BDHE assumption, the security analysis showed that the proposed scheme is secure against chosen-ciphertext attack (CCA) under the standard model.

Proxy re-encryption allows a proxy to convert a ciphertext related to a certain access policy into another one with a different access policy without uncovering the underlying plaintext, which makes the proxy re-encryption technology to be an important technology for data sharing between users.However, the proxy re-encryption schemes are mostly based on single authority, which have some problems such as single power and performance bottleneck of the authority organization and high computing burden on user’s client.At the same time, most schemes do not have the five basic characteristics of proxy re-encryption: one-way encryption, non-interaction, repeatability, controllability and verifiability.In order to solve these problems, a CP-ABE proxy re-encryption scheme for cloud computing based on multi-authority with repeatability and controllability was proposed.Based on the ciphertext policy attribute encryption scheme, proxy servers of encryption and decryption were introduced to reduce the computing burden on the user’s client, and multi-attribute authorization were set to disperse the authority of the central authority.The proxy re-encryption was improved from multiple aspects.Random factors and ciphertext sub-item set in the re-encryption key can realize one-way encryption and controllability.The re-encryption key was independently generated by the client without the participation of servers, which can support users to share data when the data owner is not online.Encrypting the ciphertext sub-item set in the initial ciphertext many times can achieve repeatability.The verification sub-item set in the initial ciphertext allowed the user to verify whether the outsourcing and re-encryption results were correct.Compared with other schemes, the user’s client computing overhead of the proposed scheme was small, and the user can decrypt the original ciphertext only by performing constant times of exponential operation.Based on q-parallel BDHE assumption, the security analysis showed that the proposed scheme is secure against chosen-ciphertext attack (CCA) under the standard model.