Research On Design And Security Analysis Of Public Key Encryption With Keyword Search

With the rapid development of cloud computing and the advent of the era of big data,massive amounts of data continue to increase,and a variety of clata(social network data,scicuitific observation data,sensor detection data,mobile positioning data,etc.)are pouring into everyday work and life.These massive,high-speed,diverse,and complex data place higher requirements on people's data storage and data processing capabilities.The advent of cloud storage has enabled users to free up local physical storage and made up for the lack of storage space.Users pay for services to save data to cloud server.Since cloud storage is provided by a third party,and there may be privacy and confidential information in the user's data,to ensure the privacy of the user,when uploading the data to the cloud server,the user first enerypts the data to ensure the data security and privacy in the cloud.But uploading enerypted data to the cloud server at the same time makes it difficult to retrieve the target file,and it is difficult to achieve simple retrieval as in plain text data.A simple method is to download all encrypted data in the cloud and send it to the data user,and then the data user decrypts it all.After obtaining all the unencrypted data,the user can retrieve the document using plaintext information retrieval.However,this strategy requires significant communication,storage,and computational costs.How to efficiently search encrypted data without decrypting is an important problem that to be solved in the era of big data.Searchable encryption(locating target data in the form of ciphertext)is the theoretical and technical basis for achieving the above functions.Searchable encryption is mainly divided into two technologies,which are symmetric searchable encryption and public key searchable encryption.This dissertation focuses on the category of public key searchable encryption.The public key searchable encryption scheme can realize two functions of data sharing and retrieval in data ciphertext.During the search process of the cloud server,since the data is out of the user's physical control,and the details of operations within the cloud platform are opaque to the user,various motivations make the behavior of the cloud server may be dishonest.This dissertation focuses on the security and privacy of keywords,two types of keyword guessing attacks,the confidentiality of data and the verifiability of results and multi-authority attribute-based searchable encryption without central authority.Around these issues,we propose the corresponding public key searchable encryption scheme,and give formal proof and efficiency analysis under the corresponding security model,the main research content:(1)Public key encryption with keyword search scheme that resists keyword guessing attacks:Keyword guessing attacks can be divided into two categories.One is off-line keyword guessing attacks,of which it is also divided into off-line keyword guessing against external adversaries and off-line keyword guessing attacks against internal adversaries,and another type is online keyword guessing attacks.To resist off-line keyword guessing attacks against external adversaries,we generate key pairs for the server and the scheme satisfies trapdoor indistinguishability to resist off-line keyword guessing attacks.In order to resist off-line keyword guessing attacks against internal adversaries,we start from the server to complete the matching test algorithm and know the disadvantages of the correspondence between trapdoor and keyword ciphertext.We divide the server into two types of servers,forward server and backward server,and any single server cannot independently complete the search and test algorithm,so there is no correspondence between trapdoor and keyword ciphertext,therefore,any server cannot launch an off-line keyword guessing attack.For online keyword guessing attacks,we use the strong computing power of the cloud server to re-encrypt the encrypted data to obtain the double-encrypted data.The double encrypted data satisfies ciphertext indistinguishability,therefore,external adversaries cannot initiate an online keyword guessing attack.In order to improve the efficiency of the scheme,we eliminated the bilinear pairing to construct only on general prime factorial cyclic group,so the efficiency of the scheme was improved.(2)Public key searchable encryption with public verifiability:When performing an encrypted keyword search,we usually assume that the cloud server is honest but curious,that is,the cloud server honestly performs search operations but it curious the result.However,in practical applications,users do not have physical control over the data.The data is stored in the cloud server,which is also managed and operated by the company.Companies may delete data for their benefit to operate and manage it.When a user performs a search operation,the server may return some incorrect search results to deceive the user.Since the user does not know the content of the data file,or even whether the data file corresponds to the keyword This poses a privacy threat to the user to a certain extent.Therefore,if the encrypted search scheme can provide the integrity and correctness of the data file,the research will play a vital role for the user.Public key searchable encryption can authorize the cloud server to perform keyword search in the keyword ciphertext index.However,in the actual cloud environment,only the public key searchable encryption with the keywords ciphertext index cannot be run alone,and it is necessary to cooperate with the data encryption corresponding to the keywords to form a complete encryption system.In this dissertation,we build a new searchable encryption scheme that combines public key encryption scheme with public key searchable encryption scheme.In terms of security,this dissertation achieves security of the document indistinguishability against chosen ciphertext attack(IND-CCA),keyword indistinguishability against chosen keyword attack(IND-CKA),trapdoor indistinguishability,against swapping attack and off-line keyword guessing attacks against external adversary.More importantly,when the server is not trusted,our scheme achieves the correctness and completeness verification of search results and satisfies the public verifiability security of search results.(3)Keyword-decryptable public key encryption with keyword search:When we use the public key searchable encryption scheme,the cloud server performs keyword search operation and returns an encrypted data file corresponding to the keyword,and the keywords ciphertext index is not returned.Due to the cloud server's own interests,the cloud may return data that is not corresponding to the keyword,therefore,the cloud server should be defined as a dishonest model.Under the architecture of public key encryption with keyword search,the data sender sends the data ciphertext to the data receiver through the cloud server.During the whole process,the data receiver and the data sender do not have any interaction,and the data receiver naturally does not know the correspondence between keywords and data files,therefore,in the case of the dishonesty of the server,the data receiver does not know the correctness of the returned data.file,which brings harm to the data security to a certain extent.If the encrypted search scheme can provide keyword decryption service and determine the correspondence between the returned data files and key words,it will help the scheme to further improve security.In the general public key encryption with keyword search scheme,the data receiver does not obtain the index ciphertext and the index ciphertext is one-way encrypted,the data receiver cannot obtain the keyword plaintext,therefore,it is also impossible to determine whether the data file corresponds to the keyword.In this dissertation,we propose a new keyword-decryptable public key encryption with keyword search supporting the keyword search and keyword decryption,therefore,the scheme further improves the security and functionality.In terms of security,we prove that our scheme is indistinguishability against chosen keyword ciphertext attack,trapdoor indistinguishability,and off-line keyword guessing attacks against the external adversary.(4)Multi-authority attribute-based searchable encryption without cen-tral authority:In the process of researching searchable encryption,we found that public key searchable encryption cannot achieve fine-grained access control of ciphertext data,and the application scenarios are limited to multiple senders-single receiver scenario.Attribute-based searchable encryption can achieve fine-grained access control of ciphertext data and satisfy the keyword search function.We have found that attribute-based searchable encryption scheme is unrealistic to use a single attribute authority to manage a large number of attributes,and existing multi-attribute schemes often require a central authority with an honest and credible nature to manage.We call this named a central attribute authority.The central attribute authority is responsible for the security of the multi-attribute scheme.If it is compromised,the security of the multi-attribute scheme will be affected.Therefore,the multi-authority attribute-based searchable encryption without central authority scheme is studied.This dissertation proposes a multi-authority attribute-based searchable encryption without central authority scheme,and removes the central attribute authority.In terms of the security of the scheme,the scheme satisfies the selected attribute set indistinguishability of chosen keyword attack and the trapdoor indistinguishability.In summary,the research work of this dissertation mainly focuses on the security,efficiency and functionality of public key encryption with keyword search,mainly focuses on solving two types of attacks on keyword guessing attacks,the data confidentiality and the verifiability of results,and removing central authority for multi-authority attribute-based searchable encryption.In view of the above problems,the provably secure cryptographic scheme in this dissertation provides a theoretical basis and also provides a reference for the ciphertext retrieval technique in the cloud.