Two level phase retrieval in fractional Hartley domain for secure image encryption and authentication using digital signatures

A novel image authentication scheme based on two level phase retrieval algorithm (PRA) propagated in fractional Hartley transform (FrHT) to extract two phase-only masks (POMs) is proposed. PRA is based on iterative phase mask which uses nonlinear process to generate POMs which in turn makes the system immune to chosen plaintext attack (CPA) and known plaintext attack (KPA). Random amplitude mask (RAM) and random phase mask (RPM) are used as encryption keys which makes the system immune to special attack. Further multiple level of security leads to the achievement of non-convergence of MSE and good performance in the retrieval process. Apart from encrypting the information, authentication has also been included in the scheme. The features incorporated in any plaintext have been shown to provide unique signatures, which can be used to verify their authenticity. The content of the original images can be authenticated only if the authentication key is correct. The robustness of the proposed multiple level cryptosystem has been examined based on various parameters by simulating on MATLAB 9.4.0 (R2018a). The experimental results highlight the suitability and shows the attacker cannot recover the original image without the knowledge of POMs. The scheme has also been compared with similar algorithms which proves that the proposed two-level scheme is more secure, feasible and effective.