Study On Hierarchical Attribute-Based Encryption System

With the continuous development of network technology,people's dependence on the network is increasing day by day.Although it provides much convenience for network users,it also brings some potential safety hazard.Therefore,the study of cryptography has become the core measures to safeguard network data security and it has also become a research hotspot.Attribute-based encryption technology is a kind of encryption technology that is available for many-to-many,and users can obtain their security keys corresponding to their own attributes.But only when their attributes satisfy the access structures of the encrypted data,can they decrypt the message.The attributes in the previous attribute encryption scheme belong to the same level and there is no difference between their importance.However,in practical applications,the attributes may be divided into different levels according to their importance in attribute set.The encryptor encrypts a message to a user who owns a certain set of attributes in the system and the ciphertext contains a hierarchical access structure.The message can be decrypted only when the user's attribute hierarchy conforms to the layering of the access structure.This paper focuses on the revocable hierarchical attribute-based encryption and unauthorized hierarchical attribute-based encryption.Specific research work are as follows:(1)Based on the ciphertext-policy attribute-based encryption(CP-ABE)scheme of Waters et al.,using bilinear pairings,a revocable hierarchical attribute-based encryption scheme under the standard model is proposed.The formalized definition and security model of the scheme are given firstly and then the concrete construction scheme.Based on the p-BDHE hypothesis,the scheme is proved to be correct,revocable,and unforgeable.Analysis shows that compared with the same type of scheme,the proposed scheme reduces the storage overhead and communication overhead,thus improving the efficiency.(2)Based on the bilinear pairings,an unauthorized hierarchical attribute-based encryption scheme is proposed in the composite order.Firstly,the formalized definition and security model of the scheme are given.Second,the concrete construction scheme is given.Finally,under the three static assumptions,the bilinear system encryption technology is used to prove that the scheme meets the requirements of indistinguishability under the attack of the adaptive selection plaintext.The analysis shows that the authorization center is not needed in the proposed scheme.And it solves the key escrow problem and makes the access strategy hidden at the same time.