Research On Multi-keyword Searchable Encryption In Cloud Environment

In the era of big data,massive data sharing greatly facilitates the lives of users,but at the same time,it also brings huge pressure on users for local storage and later main-tenance.Due to limited local disk space,more and more users outsource personal data to cloud servers for storage,thereby enjoying the efficient and convenient data management services brought by outsourced storage.However,the cloud storage model also has some data security risks.The complexity of the cloud environment makes cloud servers vul-nerable to attacks by online adversaries.In addition,the cloud server is an independent and not fully trusted entity.To protect personal privacy,user data is usually encrypted be-fore being outsourced for storage.However,this also makes it a challenge for users to effectively retrieve personal data,reducing the availability of outsourced data.Searchable encryption technology allows users to retrieve the cipher text stored on the cloud server without revealing the user's query information and retrieval results.In the context of the above-mentioned data outsourcing storage,this thesis studies the searchable encryption of outsourced data in the cloud environment to support fine-grained retrieval control and integrity verification of retrieval results.The main research results of this thesis are as follows:(1)In order to enhance data retrieval control,we have combined searchable encryption schemes with purpose-based access control.our scheme provides fine-grained ac-cess control by matching the intended purpose of the data with the preset purpose of the actual user.In addition,the TF-IDF(term frequency–inverse document fre-quency)model is used to calculate the the relevance of documents and user query keywords,thereby returning results highly relevant to user query keywords.The clustering algorithm is used to generate the index structure for ciphertext retrieval,so that this scheme can support multi-keyword ranked search,which makes this scheme take into account both efficiency and functionality.(2)For a ”semi-honest but curious” malicious cloud server,Our proposed scheme sup-ports data users to verify the search results,which ensures the correctness and com-pleteness of the search results returned to the user will not be affected by the mali-cious behavior of the cloud server.At the same time,with the help of blockchain and smart contracts,the existing use model of pay-as-you-go is changed to the model of pay-after-use which enable users to obtain a more fair experience.