Research On Multi-user Searchable Encryption Schemes In Cloud Computing

With the rapid development of cloud computing,its low cost,on-demand service and high reliability have brought great convenience to people and have attracted more and more individuals and enterprises to store data in the cloud.But in the practical applications,it will bring some security problems when the data is out of the user's control.Therefore,we have to ensure that the data on the server is stored securely.According to traditional encryption methods,data retrieval is very difficult,which brings great inconvenience to the users.Therefore,some researchers have proposed searchable encryption to solve the problem of encrypted data retrieval.The searchable encryption mechanism can be divided into two categories: symmetric searchable encryption and asymmetric searchable encryption.This paper mainly aims at asymmetric searchable encryption mechanism under the multi-user scenarios.Most of the existing schemes generate deterministic trapdoor,which makes it vulnerable under keyword-guessing attack.Adversaries can easily guess the keyword in the trapdoor via limited keyword space and bilinear map.To solve this problem,we expect to propose more efficient schemes to resist keyword-guessing attack in the sense of data sharing.The main work of this paper is as follows:First,in view of the vulnerability of existing schemes,we propose a multi-user searchable encryption scheme which resists keyword guessing attack,and enhance the threat model which regard the server as an attacker.In this scheme,different keys are used to encrypt different files.The public key of data owner is embedded in trapdoor,which specifies the data owner of searching data.Access control is achieved through data owner's authorization to users.A legitimate user only need to submit one trapdoor to access all files of the data owner with search permission.At the same time,the security and feasibility of this scheme are further illustrated by the security proof and performance analysis.Second,based on the scenarios that multiple data owners share their data with a group of users,we propose a searchable encryption scheme with a designed server.This scheme solves the problem that the number of trapdoors increases linearly with the number of documents or data owners.A user can retrieve all the files he has search privileges by submitting a single trapdoor.In the generation of index and trapdoor,we need to embed the server's public key,and the retrieval can only be done by the server with the corresponding private key.At the same time,the security and feasibility of the scheme are illustrated by the security proof and performance analysis.