Attribute-based Encryption Algorithm

As the development of the Cryptography, attribute-based Encryption, an extension from the Id-based encryption is now drawing more attention from researchers in this community for its specific practicability and scenario. The users in attribute-base encryption system are not described by Identities or certifications any more but a set of attributes. The encryption course or decryption course is related to a so called access structure. We can define the access structure to associate the set of attributes.Currently, the attribute-based encryption has reached a lot of achievements, such as the policy definition of the attribute-based encryption: ciphertext policy attribute-based encryption and key policy attribute-based encryption; attribute-based digital signature scheme; strong secure proof model applied; and multi-authority attribute-based encryption. These aspects all contribute a lot to the attribute-based encryption. However, there are still some problems involving in these methods, which includes: the improvement of the efficiency of the calculation, how to decrease the calculation times of bilinear pairings; how to improve the express ability of the access structure, how to construct more expressive monotone/non-monotone access structure based on the threshold gate AND gate and OR gate; how to construct more practical attribute-based encryption systems; how to simplify the relations between key and cipheretext; how to decrease the size of the ciphertext space and key space This article will show the research work based on the questions mentioned in the above. First we will bring in the attribute based encryption and its significant meaning. Then we will introduce the current schemes of the attribute-based encryption and make comparisons. After that, we will also introduce multi-authority attribute-based encryption and attribute-based digital signature. Further, we will show a new constructed multi-authority attribute-based encryption based on the access structure from Waters[10] plan and give a security proof with the adaptive selective set of attributes.We then extend the newly contrived multi-authority attribute-based encryption and apply it into the private information retrieval scenario. This scheme is practical and efficient. Finally we improve the scheme by using SPIR[15] scheme and make improvement on the security attribute and practicability.