Image encryption and steganography using chaotic maps with a double key protection

Abstract

In this study, we propose a complete system which uses both image hiding and image encryption techniques followed by decryption in order to meet the requirements of a secure image transfer. Chaos based cryptographic algorithms are efficient ways to develop secure image encryption techniques as they have many important properties, such as the sensitivity dependence on initial conditions and system parameters, pseudorandom property, non-periodicity and topological transitivity. Thus in our study we have developed the image encryption algorithm based on the chaotic logistic map and cat map. For this, a secret key is used to determine initial conditions and the input to the chaotic map function. The Lorenz map is then used for successive pixel encryption. Also, to make the cipher more robust against any attack, the secret key is modified after encrypting each pixel of the image using Arnold’s cat map. The encrypted image is then hidden using a steganography technique that uses a cover image along with the Lorenz map to determine the location of the pixels to be hidden in the cover. Decryption follows the exact inverse of the above mentioned technique. The image is first encrypted and then hidden with two stages of encryption to the key in order to provide additional security. The results of security and key sensitivity tests show that the proposed image encryption scheme provides an efficient and secure way for real-time image encryption and transmission.