The Research On Certificateless Public Key Encryption With Keyword Search

At present,many cloud storage platforms focus on content storage,such as Baidu cloud.In order to achieve sharing,these platforms adopt plaintext formate storage for content.Thus,they lack protection for user's content.Other cloud storage platforms such as Nut cloud adopts encryption method for user's content while she/he uploads her/his content.Concretely,the encryption procedure is performed in the cloud server to ensure the user's privacy in Nut cloud.However,when the cloud server is corrupted,the user's content will be leaked.To avoid this situation,some cloud storage platforms such as Wuala cloud adopt another encryption method which is user encrypts her/his content in client and then uploads the encrypted content to the cloud server.However,in this kind of cloud storage platforms,they do not provide searching encrypted content functionality.That is to say in the existing cloud storage platform,there is no platform that is stored in the form of ciphertext and provides a keyword search function.Considering the advantages of certificateless cryptosystem and the existing problems in cloud storage,we design a key search scheme based on certificateless public key cryptosystem,which combines certificateless cryptosystem and keyword search encryption.We hope this scheme can be used to the cloud platform to slove the searching encrypted content problem.In this dissertation,we study the concept of public key encryption with keyword search(PEKS)and certificaltelss cryptography to design a cerfifecateless PEKS scheme or called CLPEKS for short.In 2004,Peng et al.proposed the first CLPEKS scheme.However,we find some security weakness in their scheme.Concretely,their scheme suffered from two types of off-line keyword guessing attacks.In this dissertation,we propose the mentioned two attacks and then provide an improvement based on their scheme.Meanwhile,we also demonstrate the security of our improvement by formal security proofs.In the performance analysis,we find our improvement has a higher compuataional costs.Thus,we design a new CLPEKS scheme in this dissertation.We also define a new model,adversarial model,and security notions for CLPEKS.We demonstrate the security of our new scheme in the random oracle model and under the bilinear Diffie-Hellman(BDH)and the computational Diffie-Hellman(CDH)problems.Finally,we simulate a cloud platform in Windows and performs the proposed two schemes in the platform.The experimental results analysis shows that our CLPEKS 2has a better performance.Compared with the recently proposed PEKS schemes,our CLPEKS2 has a better performance and security properties.Finally,we build a cloud platform in Windows system for simulation experiments.After the experimental analysis,we found that Peng's improved algorithm,although in terms of security has been sufficiently guaranteed,but in the computing efficiency and search time is not ideal.Our proposed new method has higher search efficiency and lower computational cost.Experimental results show that our new method has better performance and solves the cumbersome certificate management in the traditional public key system and key escrow in the identity-based key system.