Design And Implementation Of Outsourcing Ciphertext Calculation Scheme Based On Function Encryption

Cloud computing has huge computing power and storage space,providing users with a variety of fast and convenient services.However,due to the data needs to be sent to the cloud server,it may cause the leakage of user privacy.At present,it is generally believed that the most direct and effective way to protect the privacy of data is to encrypt the data and then upload it to the cloud server.However,it also brings a new problem,that is,how to calculate the encrypted data.Homomorphic encryption can be used to calculate ciphertext data,but it is still a ciphertext result after calculation.In some scenarios,users hope that the cloud server can directly get a plaintext result after computing the ciphertext data,and the cloud server makes some decisions based on the plaintext results,so homomorphic encryption does not apply to these scenarios.Function encryption is a new hotspot in public-key cryptography.Function encryption generates different decryption private keys according to the different calculation functions of ciphertext data.The cloud server with these private keys decrypts the ciphertext and gets a function value about the plaintext instead of directly getting the plaintext itself.The function value is in plaintext form and is equivalent to the result obtained by computing the plaintext directly.Therefore,this paper proposes an outsourcing ciphertext computing scheme based on function encryption for the calculation of ciphertext data in the cloud environment.This paper first proposes a single-user scheme,which is mainly divided into two parts: singleuser outsourcing ciphertext computing framework and function encryption algorithm.In the function encryption algorithm,the garbled circuit module is improved to speed up the decryption of encrypted data.Based on the single-user scheme,a multi-user scheme is proposed.The multi-user outsourcing ciphertext computing framework is a two-stage encryption and decryption framework based on the single-user framework.The framework is mainly divided into four steps: one-stage encryption,two-stage encryption,one-stage decryption,and two-stage decryption.One-stage encryption and two-stage decryption are one encryption scheme,two-stage encryption and one-stage decryption adopt function encryption algorithm based on inner product operation.Compared with the single-user framework,the framework adds two processes: one-stage encryption and two-stage decryption.This paper designs the two processes accordingly.In one-stage encryption,the random number is added to each plaintext data to avoid the problem of a large amount of calculation in the traditional encryption algorithm.In the second stage of decryption,a specific private key is designed to eliminate the influence of the random number.Using nested encryption,the framework can avoid the leakage of some plaintext information and improve the speed of ciphertext calculation.Finally,this paper implements and analyzes the designed single-user and multi-user solutions.