A Research And Application Of High Efficient Hierarchical Attribute-based Encryption

With the rapid development of cloud computing in recent years,the storage of local data in high-performance and cost-effective cloud servers,which could reduce the cost of local data storage and management,has become the first choice for more and more individuals and enterprises.Considering the security requirements of users on cloud servers and the untrustworthiness of cloud servers,a secure data sharing scheme for cloud storage has been widely studied by using ciphertext policy attribute based encryption(CPABE).The CP-ABE encryption system replaces user identity with user attributes,as a result only the attributes information would exposing in the system,which is flexible to deal with the problem of identity privacy.However,there are some serious problem when encrypting the files with hierarchical structure,such as the difficulty to control users,the complexity of encryption and the overload of computation and storage.A series of researcher are launched in this paper to solve above problem.Considering the basement of the ciphertext policy hierarchical attribute-based is CPABE,this paper would focus on CP-ABE scheme firstly.In order to implement the finegrained control of users,an user revocation mechanism are included in the CP-ABE scheme.Due to the complexity of the local calculation in the encryption/decryption process,it would take quiet a plenty of time to encrypt and decrypt which is a burden for the system.To resolve the problem,a third party servers would be introduced in this paper to reduce the burden.Based on the CP-ABE study,this paper makes a deep research on the CP-ABE encryption scheme with a hierarchical structure and achieves the following results:(1)In this paper,we propose a CP-ABE encryption scheme for outsourced encryption and decryption of users(RO-CP-ABE)based on the Chinese remainder theorem and ciphertext updating.This scheme realizes that the revoked user cannot decrypt the ciphertext by updating the ciphertext stored in the cloud server.At the same time,this solution combines the idea of key splitting to split the user private key into an outsourced decryption key and a local decryption key.And then,outsourcing the complex computation to the third party server to reduce the burden of local encryption and decryption.Finally,the CPA security model are used to analyze the security of the program and the performance analysis are executed at the same time.(2)This paper proposes an outsourced decryption and hierarchical ciphertext policy attribute based encryption scheme(ROFH-CP-ABE).This scheme can encrypt files with hierarchical structure efficiently.At the same time,this solution reduces the time for user decryption by outsourcing the complex decryption process to the decryption server.The user revocation is implemented by updating the encrypted files,ensuring that the revoked user cannot decrypt the ciphertexts.Finally,it can be declared that the proposed scheme is efficient and feasible through the analysis of the experimental results.On this basis,this paper analyzes the security of the scheme deeply.