Privacy preserving cloud based secure digital locker using Paillier based difference function and chaos based cryptosystem

In this paper, a cloud based digital image locker system along with secure user authentication and novel image cryptosystem for preserving privacy of user images is proposed. Images require more storage space as compared to text. So, it is not feasible to store images locally in digital locker for everyone. By taking advantage of high speed Internet, it is feasible to use cloud for efficient storage of images. However, so many researchers feel that cloud technology is ‘honest-but-curious’. Cloud service follows the specified protocol completely, but it traces and analyzes the data to get the user's important information. To overcome from such challenges, privacy of user's identity and data should be preserved. The proposed authentication protocol is designed using Paillier based difference function which is based on Homomorphic cryptosystem. The speciality of homomorphic function is that computation on encrypted data is possible without decrypting the cipher text. Because of this, authentication process is done in encrypted environment. A novel image cryptosystem is designed based on Fridrich model. In this cryptosystem, confusion is performed at bit-level and diffusion is performed at pixel-level. Keys are modified in each round of confusion to achieve more security. Simulation and cryptanalysis prove the effectiveness of the proposed system. © 2020 Elsevier Ltd