Research On Public Key Encryption With Authorized Keyword Search

With the rapid development of cloud computing,more and more people upload data to cloud servers for data storage and sharing.In order to protect the privacy of data,users usually encrypt the data firstly,then upload the ciphertext to cloud servers.Encryption technology protects the privacy and integrity of data,but not conducive to data retrieval.Searchable encryption allows users to retrieve on ciphertext without decryption.This paper starts from the application scenario of multi-user data sharing,proposes two public key encryption with authorized keyword search schemes,and describes them in detail.The specific contributions are as follows:Firstly,we propose a specific scenario of multi-user data sharing,and construct a revocable public key encryption with authorized keyword search(RPEAKS)scheme according to the requirements of the scenario.In the scheme,the data sender only needs to encrypt the shared data once.If the user without the corresponding private key wants to retrieve on the ciphertext,he must be authorized by the manager.The manager grants users search rights on a particular keyword set by sending an authorized token to them,and the size of the authorized token is constant,independent of the size of authorized keyword set.Each user has his own decryption key and authorized token,he can only search keywords in the authorized keyword set without sharing authorized token and decryption key with others.Once the user's search right changes,such as: retirement,the manager can revoke his search right efficiently and flexibly.Secondly,considering the trust of PKG and the problem of collusion among malicious users,we construct a traceable and revocable public key encryption with authorized keyword search(TRPEAKS)scheme.In addition to supporting flexible revocation of users' search rights,the scheme also supports weak black box tracing for malicious usersand PKG.Besides,in the scheme,the user can get a single decryption key without concealing to the PKG which key he obtained,which further protects the privacy of the user's decryption key and reduces the trust of the PKG.