Research And Application Of Supporting Policy Hidden Attribute-based Encryption

The attribute-based encryption system of the hidden policy is a cryptographic system for applications where the security requirements are relatively strong.In a policy-hidden attribute-based encryption system,an encryptor can encrypt the data using the attributebased encryption system so that he can flexibly share the data,but he does not want anyone to know which users he shared at the same time,so that some malicious users to guess the data,reveal some of their sensitive information.The system can not only encrypt the data,but also encrypt the access policy.It has been a hot topic in cryptography and information security since Nishide et al.proposed the first hidden policy encryption scheme in 2008.Because of the high academic and application value of the attribute encryption of the hidden policy,this thesis has carried on the thorough research,and obtains some achievements on research.Hidden policy of the attribute-base encryption system has been put forward,there are many researchers to study it,the relevant research results continue to emerge.In this thesis,we will summarize the research results of the attribute-based encryption system of hidden policy,summarize the present research situation from the aspects of definition,function,expression of access structure and security of the scheme,and make a simple review of the existing scheme and comparison.In this thesis,we propose a policy-hidden attributebased encryption scheme,and give its formal definition and security model.Then,this thesis constructs a policy-hidden attribute-based encryption scheme,and proves that it is fully secure.Finally,this thesis compares the other policy-hidden attribute-based encryption scheme,expounds the advantages of the scheme,and verifies that the scheme improves the efficiency of user decryption compared with the original scheme.Many of the existing policy-hidden schemes are based on the bilinear group of composite order.It is well known that the performance of bilinear group with composite order is worst than the prime order.In order to achieve the same security level,it needs 160 bits in prime order bilinear group,while 1024 bits in composite order bilinear group.Therefore,the most of the current policy-hidden attribute base encryption schemes are faced with an efficiency problem.This thesis proposes a policy-hidden attribute base encryption scheme with a constant amount of computation,and gives its formal definition and security model,and proves it is fully secure in the standard model,and finally we will give an experimental verification.What we need to know is that the policy hidden attribute-based encryption that this thesis study is a kind of ciphertext policy attribute-based encryption(CP-ABE).Overall,the shadow properties of the access policy attribute-based encryption future was promising and has very high academic research value and worth further study.