Abstract:

A novel image steganography was proposed，which was based on nonsubsampled Contourlet transform （NSCT）and Hill cipher.Firstly，cover image was decomposed with NSCT.It provided a multi-scale and multi-directional representation of an image.One of subbands was selected to embed secret data.Then Hill cipher was applied to encrypt the secret message.How to find a proper cipher matrix was important in this way.The selected matrix should be inevitable and relatively prime to the number of alphabets.The skill of 2^k correction was applied to ease the difference between cover and stego image.Experiment results show that both stego image and retrieved image have better image quality with the proposed approach than other methods.

Key words: NSCT, Hill cipher, 2^k correction, cipher matrix