Research And Design Of Security Protocol Based On Homomorphic Cryptography

Data island means that in order to protect data security,all data owners protect their own data and do not interact with the outside world.Data security is the key to ensure business security and personal security.The strengthening of data protection also makes the phenomenon of "data island" more and more obvious.However,in reality,enterprises and organizations often realize business cooperation through data interaction.Therefore,in order to promote business development,eliminating data islands has become an urgent need,which also makes the research of cryptography algorithms in data privacy protection become a hot spot.Among them,homomorphic cryptography is one of the key technologies to solve the data island.Homomorphic algorithm has the characteristics that the operation of ciphertext is equivalent to the relevant operation of the corresponding plaintext.In order to take advantage of the powerful computing power of cloud service providers,we can safely store the ciphertext data to the cloud computing platform and calculate and process the ciphertext data,so as to avoid the risk of data leakage caused by the direct contact of unsafe third-party cloud computing platform with plaintext data.According to the security characteristics of homomorphic cryptography algorithm,this thesis combines homomorphic cryptography with digital watermarking,secure multi-party computing and lattice cryptography to design several security protocols suitable for different scenarios.The main research results are as follows:(1)Based on the Paillier homomorphic cipher algorithm in cryptography and the state secret SM4 block cipher algorithm,the least significant bit(LSB)is used to embed double watermarks in the wavelet transform domain,and an innovative double watermarking algorithm in the ciphertext domain is proposed.By selecting the horizontal high frequency LH3 and vertical high frequency Hl3 of the triple wavelet transform,the watermark is embedded,and the rest is encrypted with SM4.In this part,the watermark is embedded by Paillier algorithm,and its additive homomorphism is used to finally generate an effective ciphertext with watermark.When extracting the watermark,according to the mapping relationship between ciphertext operation and plaintext operation in additive homomorphism,the watermark can be successfully extracted by performing correlation operation on the decrypted data.Experimental simulation data show that compared with the existing schemes,the protocol has fast operation speed,high quality of watermark extraction and good invisibility of the embedded image.(2)Based on homomorphic cryptographic algorithm,oblivious transfer idea and symmetric cryptographic algorithm,an anonymous query protocol is constructed,which is suitable for multi-party data sources.The protocol can query data in multiple data sources while protecting the privacy and security of user data.Firstly,the anonymous query protocol model based on three parties is introduced,and the specific process is introduced in detail.Then,the correctness and security of the protocol are analyzed theoretically,and the corresponding experimental simulation is carried out.Finally,based on the three-party anonymous query model,a multi-party anonymous query protocol is proposed and introduced in detail,and the specific application of the protocol is proposed.It can screen blacklist users in data transactions,evaluate users' reputation,and alleviate users' malicious purchase of electronic products.The experimental simulation results show that the theoretical operation results of the protocol match the actual operation results,and the operation efficiency is high.(3)Based on the LWE difficult problem,a new homomorphic cryptographic algorithm is designed.Firstly,aiming at the problem that Regev can only encrypt a single 0 or 1 bit,the Regev scheme is improved,an encryption scheme based on Regev integer domain is proposed,and the correctness and security of the algorithm are proved.Secondly,an additive homomorphic algorithm is constructed based on the algorithm,and the correctness of the algorithm is proved by arithmetic derivation and code implementation.The homomorphic algorithm can carry out multi-level homomorphic addition under certain parameter limits,and has certain application value.Finally,the homomorphic cryptographic algorithm based on lattice is used to replace the homomorphic cryptographic algorithm in the above two protocols,so that the protocol has certain anti quantum attack,and the time load of the anti quantum protocol is analyzed.