A Selective Image Encryption Scheme Based on 2D DWT, Henon Map and 4D Qi Hyper-Chaos

In recent years hyperchaos has found applications in several fields such as medicine and engineering. It has been applied in image-based applications which require reliable, fast, and robust security systems to store or/and transfer images. Given the increased use of images, there is a fundamental requirement among security in ensuring protection, confidentiality, privacy, integrity, and authenticity of such images. This, in essence, has become a major concern. Many preventive and protective algorithms, including chaos-based schemes, have been developed over the past years in trying to prevent directed attacks. However, many existing chaos-based encryption schemes have been successfully decrypted. One of the main reasons for these chaos-based image encryption schemes being successfully attacked is that the degree of randomness of the chaotic system used is not high enough to guarantee robust encryption. The key space lengths of many of the existing cryptosystems are not long enough to guarantee the desired security properties of chaos-based ciphers. Thus, the security level is lowered. In this paper, a selective image encryption algorithm based on 2D Discrete Wavelet Transform, Henon's Map and 4D Qi Hyper Chaos is proposed. This paper is developed such that 2D DWT is used to decompose the image into details and approximations, Henon chaotic map is used to shuffle the decomposed image pixels' positions. The shuffled image is further encrypted with the bit streams generated by Qi hyperchaos using XOR operation. The experimental results demonstrate that the proposed algorithm provides a large key space, high security, and resistance to different types of attacks. When compared to some existing algorithms, the performance of the proposed method displays a better performance with respect to security and encryption making it suited for real-time applications.