Research On Security Theory Of Proxy Re-encryption Based On Lattice

In the wake of developments in cloud computing technology,a growing number of users choose to store their data files on the cloud server.Cloud storage not only provides users with convenient and efficient data storage services,but also accelerates the sharing and use of data.In fact,cloud service providers are not completely trusted,so users' data security and privacy protection have become a widespread concern.The proxy re-encryption technology is a natural application for cloud storage.By using the proxy re-encryption technology,one user's ciphertext stored on the untrusted third-party cloud server can be transformed into another user's ciphertext without decryption,which realizes the data security sharing in the open network environment.In recent years,the lattice public key cryptosystem based on the worst-case lattice problem has attracted extensive attention in the field of cryptography.Not only because most of the operations in the lattice are linear operations,the calculation is relatively simple,more importantly,the lattice cryptosystem is considered to be the best choice against quantum computing.Therefore,in this thesis,based on the learning problem with errors in the lattice,the proxy re-encryption algorithm is studied deeply.By analyzing the existing lattice cipher algorithm and combining the characteristics of the traditional public key cipher algorithm,this paper explores the design of the lattice based proxy re-encryption algorithm which can be applied to different scenarios,so that it can not only resist the quantum attack,but also effectively reduce the burden of frequent access to account number and password.What's more,it can solve the inconvenience of users in data sharing in the cloud environment.The main research results are as follows:1.Research on identity-based proxy re-encryption on lattice: This thesis makes a profound study of the security model of identity-based proxy re-encryption.And a multi-bit bi-directional proxy re-encryption scheme based on identity on lattice is proposed,which maps user's identity information into a matrix.It makes the user's private key smaller,expands the ciphertext space,and greatly improves the encryption efficiency.What's more,it satisfies of indistin-guishability under chosen-plaintext attack in the standard model.2.Research on attribute-based proxy re-encryption on lattice: This thesis deeply studies the security model of attribute-based proxy re-encryption,and explores the similarities and differences between attribute-based proxy re-encryption and identitybased proxy re-encryption.On the basis of identity-based proxy re-encryption,the concept of attribute-based encryption is introduced.In this thesis,a unidirectional attribute-based proxy re-encryption scheme on lattice is designed.On the premise of ensuring the confidentiality of user's data file,it also realizes the more fine-grained access control of legitimate users to shared resources,strengthens the reliability,integrity and confidentiality of cloud data,and enriches the application scenarios of proxy reencryption.The scheme can not only resist quantum attack and collusion attack,but also be proven to be against chosen plaintext attack provable security in the standard model.