Attribute Revocation Encryption Cloud Sever Scheme Based On Hidden Policy In Multi-Authority

Cloud comput ing and cloud storage technologies are developing rapidly.Count less informat ion is generated and exchanged every day.These informat ion and data cannot be stored in local servers.The advent of cloud storage has provided a new world for data storage.The cloud server is honest but cur ious.In order to solve this proble m,the files must be encrypted before they are uploaded to the cloud server that stores a large number of files.It is really difficult for users to find the files they want.For this reason,searchable encryption sche mes and attribute-based encryption schemes have received extensive research and development in recent years.The attribute-based encryption scheme can solve the encryption problem of files stored on the cloud server side.The user who satis fies the access structure can decrypt the file.We use the ciphertext-based encryption scheme to solve the file encryption proble m,and the searchable encryption scheme to solve the search problem when the file is stored.The main contents of this thesis are as follows:(1)This thesis comb ines searchable encryption and search based on attribute-based encryption to achieve the search and encryption of files.A searchable privacy protection scheme based on cloud storage attribute revocation and semi-hidden construction is proposed.In order to imple ment the user attribute revocation,a subset coverage revocation scheme is used to generate a corresponding user tree for each user attribute on the original basis.Moreover,t he revocation no need to update the user key later,which reduces the corresponding comput ing cost.During t he revocation process,the multi-attribute authorit y updates part of t he ciphertext and uploads the updated ciphertext to the cloud server.Mult i-attribute authority is used to distr ibute and manage keys.At the same time,no trusted authority or mana gement aut hority is required.A secur ity proof ga me is performed to prove the ind istinguishability chosen-ciphertext policy and chosen pla inte xt attack(IND-sCP-CPA)games and indist inguishability under chosen-keyword attack(IND-CKA)games.(2)An efficie nt searchable encryption scheme based on an attribute-based encryption sche me is proposed.Part of the computation is outsourced to a trusted third-party organization,which aims to reduce the comput ing cost of users and data owners;a keyword access permiss ion index table is set.The user who searches the used keywords can directly look up the table to reduce the comput ing cost of the data owner and user's retrieva l.The CP-ABE encrypt ion scheme is used to ensure the security and efficiency of our scheme;(3)This thesis can prove that the proposed scheme has more funct ions by comparing the comput ing cost of the encryption,the decryption process,searchable encryption process,and the storage cost of ciphertext,key,key index,and threshold in similar references.This scheme takes up less storage space,and less computing cost.