Abstract
In this paper, an extended sequence using chaotic map and Bernstein form Bezier curve to improve the chaotic key sequence is presented. Based on this sequence, we perform the scrambling in DCT domain with variable control parameters. To further enforce the security, the gray values of image pixels are diffused using keystream extracted from the extended key sequence of the chaotic map and the plainimage. As a result, the algorithm resists the chosen-plaintext/chosen-ciphertext/known-plaintext attacks, as diffusion depends on the plainimage. Moreover, experimental results and analysis confirm a high security level using the proposed scheme.