| Because of the convenience and economy of cloud computing,more and more individuals and enterprises used cloud platform to store data.Moreover,due to great storage space of the cloud computing,the combination of cloud platform and big data was increasingly common.However,traditional access control technologies cannot meet the security requirement of cloud computing.They have the problems such as high cost with low efficiency,etc.Attribute based encryption is an effective solution to the security of cloud storage system.In the algorithm,every user is tagged by sever attributes.Secret key and cipher-text are related to a set of attributes.Therefore,the attribute based encryption is able to reduce data redundancy,and ease the burden of managers.While the user can control the data access flexibly and keep the outsourced data with privacy and security.This article mainly studied the attribute based encryption and introduced different types of algorithms in detail.Then we analyzed existing attribute based encryption and policy update scheme.This article proposed a new scheme of attribute based encryption and an improved policy update mechanism.The main contributions are as follows:1.Propose a ciphertext policy attribute based encryption(CP-ABE)scheme with a single authority.We mitigated the problem of heavy cost of storage,high cost of communication in CP-ABE without sacrificing efficiency and introduced the function of policy update outsourcing.Security of the scheme is proved through reducing the scheme to general group model and hash model.2.Propose a CP-ABE scheme with multiple authorities.We mitigated the problem of low computational efficiency and high cost of storage in policy update.Morevoer,we proposed a function for encryption outsourcing and decryption outsourcing which makes the system adaptable to resource-constrained devices.Security of the scheme is proved through reducing the scheme to decision subgroup problem. |
