Multiple colour image encryption using multiple parameter FrDCT, 3D Arnold transform and RSA.

We introduce a novel image encryption and decryption algorithm for multiple images incorporating multiple parameter fractional discrete cosine transform (MPFrDCT), 3D Arnold transform and RSA cryptosystem. Before encryption, the images are changed into their indexed formats by removing their color maps. The indexed formats of the images are taken as the red, green and blue channel of an RGB image. Firstly, the RGB image is taken as the input of 3D Arnold transform. The 3D Arnold transform not only dislocates the pixel positions, but also changes the pixel values. Mathematically, the 3D map performs both permutation as well as substitution. The distorted image is now encrypted using RSA cryptosystem which is a public key cryptosystem. The RSA cryptosystem makes the image secure in public domain as the hard problem is the factorization of large primes which is unbreakable. Lastly, the domain of the encrypted image is changed to frequency domain using MPFrDCT. If the secret keys are known to an unauthorized person, the encryption algorithm is still secure as the security of the presented cryptosystem depends upon the secret keys and the arrangements of the secret keys. The proposed image encryption algorithm is storage efficient. The statistical and simulation analysis are conducted to evaluate the robustness of the presented encryption and decryption processes. [ABSTRACT FROM AUTHOR]