Two-Level Image Encryption Algorithm Based on Qi Hyper-Chaos

In this paper a new image encryption algorithm is proposed based on Qi hyper-chaotic system. Pseudo random sequences generated from Qi hyper-chaotic system are used to hide the image visual information and to change the image characteristics in the frequency and spatial domains. In this method, a two-level encryption is employed. The first level consists of a selective encryption of Discrete Cosine Transform coefficients at the frequency domain using exclusive or operation. In the second level, the pseudo random sequences´ sorting is used to shuffle the image pixels in the spatial domain. The experimental results and analysis of the algorithm suggest that the proposed scheme provides not only effective encryption but also a large key space and a resistance to different types of attacks.