Research On Attribute-Based Fully Homomorphic Encryption And Proxy Re-Encryption Scheme On Lattice

In modern security research,such as cloud computing and cloud storage,one major development direction is how to ensure the secrecy of sensitive data and realize safe sharing.In addition to utilizing the cloud’s computational and storage capabilities,fully homomorphic encryption technology may process data uploaded to the cloud without revealing the user’s personal information.This not only addresses data security issues on the cloud but also makes use of the cloud’s features.Multiple users can upload data encrypted with different keys to the cloud,perform secure multi-party joint calculations on the data,and support arbitrary homomorphic operations on the ciphertext of different users thanks to multi-key fully homomorphic encryption technology.This meets their needs in a cloud environment.Fine-grained access control of shared data,however,cannot be accomplished using the conventional multi-key fully homomorphic encryption technology.Combining the benefits of multi-key fully homomorphic encryption and attribute-based fully homomorphic encryption,multi-strategy fully homomorphic attribute-based encryption technology can simultaneously achieve homomorphic operation of ciphertext under various policy attribute sets and fine-grained access control of shared data in a multi-user environment.A fully dynamic and fully homomorphic attribute-based encryption scheme on lattice that supports multi-policy and has short ciphertext is proposed by utilizing bootstrap technology and a substitution branching program in order to address the issues of large ciphertext size and a limited number of hops in the current fully homomorphic attribute-based encryption scheme that supports multi-hop and multi-policy.The method enables homomorphic computation of ciphertext with a variety of attribute sets and access control requirements.Any participant can join in on the process of ciphertext computation in real time and dynamically after the ciphertext has been homomorphically computed,as can the ciphertext of the new user and the output homomorphic ciphertext.The length of ciphertext and the storage expense of atomic homomorphic operations are only linearly related to the current number of access policies participating in homomorphic operations,and the number of access policies participating in homomorphic operations does not need to be fixed initially.Since several users exchange ciphertext data in the present cloud computing context,ciphertext conversion is required.Data in the cloud will be exposed to hidden risks such user data leakage if an unreliable cloud service provider decrypts and re-encrypts the data.The ciphertext encrypted by the authorizer’s public key is changed by the proxy re-encryption technique into the ciphertext encrypted by the acceptor’s public key.Semi-trusted agents can achieve many-to-many granular data exchange by converting the ciphertext under one access policy into ciphertext under another access policy using attribute-based proxy re-encryption technology.A fully homomorphic attribute-based proxy re-encryption scheme on lattice allowing multi-hop is developed in light of the issue that the classic attribute-based proxy re-encryption scheme can only achieve the proxy of ciphertext in the cloud but not the operation processing of ciphertext.The scheme is capable of transforming ciphertext that satisfies one access policy into ciphertext that satisfies a different access policy,and it satisfies the multi-hop property.The ciphertext can be transformed by the proxy multiple times,and both the newly encrypted ciphertext and the proxy-encrypted ciphertext are capable of performing all homomorphic operations,such as AND NOT operations.The scheme is proven to be secure against honest re-encryption attacks in the case of learning with errors issue and has a reduced private key size when compared to other similar schemes.It has higher security because even if the malicious acceptor and the partially honest agent together obtain the input ciphertext corresponding to the re-encrypted ciphertext,they are unable to obtain the authorizer’s private key.