Research And Implementation Of Ciphertext Number Calculations Based On Additive Homomorphic Encryption

As a new type of business model formed by the rapid development of the Internet,cloud computing is highly favored by users because of its powerful computing and storage capabilities.However,the issue of user data security in cloud computing has limited its development and application to some extent.The homomorphic encryption technology can directly calculate the ciphertext number and decrypt the calculations result,the decrypted data is the same as the result of the same calculations on the plaintext number.Using homomorphic encryption technology in cloud computing,users can store data in the form of ciphertext number on the cloud platform,it can realize the calculation of numbers without exposing the plaintext number and solves the data security problems effectively when users entrust privacy data and calculations to third parties.Fully homomorphic encryption algorithms can simultaneously support homomorphism calculations of addition,subtraction,multiplication,division of ciphertext number.Although it can satisfy the security of data and the ciphertext number calculation requirements in cloud computing,there is no practically usable fully homomorphic encryption algorithm at present because of its complexity and low efficiency.Partially homomorphic encryption algorithm only supports a single homomorphism calculations,which cannot satisfy the calculation requirements of ciphertext in cloud computing.In view of the above problems,combined with the security requirements and the characteristics of cloud computing,a ciphertext number calculation scheme based on additive homomorphic encryption algorithm is proposed and its specific implementation is studied in this thesis.The ciphertext number calculations include basic calculations such as the ciphertext number addition,subtraction,multiplication,division calculations and complex calculations such as power,logarithmic,sinusoidal calculations.This method achieves various computations of ciphertext numbers without an effective fully homomorphic encryption algorithm,which can meet the security requirements and computational requirements in cloud computing.Although this method is not a true fully homomorphic encryption technique,it has the property of approximately fully homomorphic encryption.Therefore,this method is a transitional scheme to a fully homomorphic encryption algorithm.Finally,a ciphertext number computing system based on the ciphertext number calculations scheme is designed and implemented in this thesis to complete the computation of ciphertext number.The innovations of this thesis are as following:(1)A ciphertext number calculations scheme based on the additive homomorphism encryption algorithm is proposed to realize the homomorphic addition,subtraction,multiplication,division,logarithmic,sinusoidal calculations of the ciphertext number while protecting user data security effectively.In the absence of a practical fully homomorphic encryption algorithm,the proposed method can meet the security requirements and computing requirements in cloud computing and is a feasible scheme.(2)Homomorphic encryption algorithm is generally for the integer domain,a ciphertext number calculations scheme proposed in this thesis can implement calculations of the fixed-point number,which extends the application range of homomorphic encryption algorithm.(3)In this scheme,the ciphertext number are segmented by using additive homomorphism of the homomorphic encryption algorithm,so all ciphertext numbers involved in the calculations are not the original ciphertext numbers in the process of calculations,which are the ciphertext numbers after being decomposed.And during the calculations,we add random perturbation data to ensure the safety of data in the computation process,thus further improving the security of the method.