New Fully Homomorphic Encryption Scheme Based on Multistage Partial Homomorphic Encryption Applied in Cloud Computing

Cloud computing is deemed as one of the most powerful innovations in the computing world, However its usage is still hindered by security concerns. Many types of encryption algorithms were applied in the cloud for securing the data. Data can be stored in the cloud in an encrypted form. So, a new technique called Homomorphic encryption is introduced that allows to apply specific operations on the encrypted data. The paper presents an overview of security issues in cloud computing and utilization of the fully homomorphic encryption technique has drawbacks of large key size and low calculation efficiency, and it is not practical for the secure cloud computing. We build up a hybrid homomorphic encryption scheme based on the GM encryption algorithm which is additively (single bit) homomorphic, and RSA algorithm which is multiplicative homomorphic. The hybridization of homomorphic encryption schemes seems to be an effective way to defeat their limitations and to benefit from their resistance against the confidentiality attacks. This hybridization of homomorphic encryption algorithm lead to increase the speed (2.9) times, reduce the computation time to 66% percentage from previous one, enhanced confidentiality of the data that is stored in the cloud by enhancing security (two layer of encryption methods used) . Since hybrid encryption is utilized high security and authentication is provided.