Secure file storage and retrieval in cloud

Security in cloud storage is an important aspect of cloud computing. In this paper, a novel multi-level encryption scheme which ensures security in cloud is introduced. In this scheme, a modified RSA (MRSA) key generation algorithm is used to generate the phase keys. The file is first subjected to encryption using MRSA with phase public keys. For secure transmission, a modified Vernam cipher (MVC) is applied to the file and stored in the cloud. Upon request, the file is obtained by applying inverse MVC followed by MRSA decryption using the phase private keys. This scheme was tested on different types of input files. The proposed algorithms protect the system from brute force attack. The MRSA's computational time is significantly less compared to the traditional RSA algorithm. Frequency and spectral analysis proves that MVC is strong and effective. Thus the new scheme ensures both confidentiality and integrity.