Abstract: In recent years, owing to frequent flow of digital images across the world over the transmission media, it has become essential to secure them from leakages. Due to the exceptionally desirable properties of mixing, sensitivity to initial conditions and parameters of chaotic maps; chaos-based encryption has recommended a new and efficient way to deal with the problem of fast and highly secure image encryption. The implemented image encryption scheme consists of an 80-bit secret key and uses chaotic map like Arnold Cat-Map and Logistic Map. The initial conditions for the chaotic maps are derived using the 80-bit secret key. In this cryptosystem, permutation-diffusion architecture followed by an efficient diffusion scheme is implemented. This scheme consists of two diffusion procedures, with a supplementary diffusion procedure padded after the normal diffusion. In the supplementary diffusion module, the control parameter of the selected chaotic map is altered by the resultant image produced after the normal diffusion operation. As a result, a slight difference in the plain image can be transferred to the chaotic iteration and bring about distinct key streams, and hence totally different cipher images will be produced. Therefore, this scheme can remarkably accelerate the diffusion effect of the cryptosystem and effectively resist differential attacks. Our project objective is to provide high level of security and satisfactory encryption speed for practical secure image applications.

Keywords: Arnold Cat- Map, Logistic Map, Chaotic map, Cipher, Permutation, Diffusion.