Research On Public Key Searchable Encryption Scheme Without Secure Channel

In the era of big data,it becomes a problem for people that how to store and deal with massive data.The emergence of cloud computing provides a new solution for this issue.As an application mode of cloud computing,cloud storage gets its popularity because of the ability to store data remotely.In order to offload local storage space,user prefer to store data to cloud server.To protect the security of data and for privacy,user usually encrypts the data firstly,and then stores ciphertext to the cloud.However,searching on encrypted data faces new problem,due to the characteristic of the ciphertext.The searchable encryption mechanism can directly search on ciphertext.Searchable encryption is classified into symmetric searchable encryption(SSE)and public key encryption with keyword search(PEKS).PEKS enables complex operations on ciphertext without exchanging keys between data owner and data user,and then it is more powerful than SSE.To prevent the leakage of trapdoor privacy,traditional PEKS assumes that there is a secure channel between the client and the cloud server to transfer trapdoors.Unfortunately,this assumption is not satisfied in practical application scenarios.In order to solve this problem in the PEKS mechanism,the notion of the secure channel-free public key encryption with keyword search(SCF-PEKS)was proposed.In the existing research,most schemes are proven secure under the random oracle model,the scheme which is constructed in the standard model is too complex and not practical.Motivated by the above issues,this thesis's works are described as following:1.This thesis introduces the development and background of the PEKS system firstly,and analyzes several classical PEKS schemes,describes the merits and defects of each scheme.Then the relationship between PEKS and identity based encryption(IBE)is described,and a generic method for converting from IBE scheme to PEKS scheme is proposed.2.Based on the Wee's IBE scheme,this article present a new PEKS scheme over the composite-order bilinear groups,and the scheme's chosen keyword attacks(IND-CKA)security is proven based on the decisional subgroup assumption in the standard model.Compared with the previous PEKS schemes,the construction of this article has advantages in terms of security model and computational efficiency.The scheme has smaller trapdoors and PEKS ciphertexts,and the test algorithm only needs one bilinear pairing operation.3.This article proposes an efficient SCF-PEKS scheme by introducing the server's public and private keys.This scheme is constructed over the composite-order bilinear groups,and the scheme's chosen keyword attack(IND-CKA)security is proven based on the decisional subgroup assumption and DBDH assumption in the standard model.The proposed scheme not only has more concise construction,but also achieves better security.The work of this thesis takes SCF-PEKS as the research object,and proposes a SCF-PEKS scheme under the standard model,which has theoretical significance.For the related applications of searchable encryption,the work of this article also has certain references.