Digital Image Steganography using a Novel Uniform Distortion Function with all Possible DCT Magnitudes

Secure steganographic algorithms hide confidential messages within other, more extensive data (carrier media). An attacker should not be able to find out, that something is embedded in the steganogram (i. e., a steganographically modified carrier medium). The existing distortion functions are minimal distortion function is used for both side-informed and non-side-informed secure JPEG steganography. UED tries to spread the embedding modification uniformly to quantized discrete cosine transform (DCT) coefficients of all possible magnitudes and achieves statistical detectability. The inappropriate use of DC and zero AC coefficients in JPEG steganography may lead to additional block artifacts in stego image and decrease in the efficiency of JPEG compression. That is why the most existing JPEG steganography schemes use only non-zero AC coefficients as possible cover elements to make the embedding naturally content-adaptive. In our proposed system, certain DC and zero AC coefficients in the texture regions could indeed be incorporated to further data embedding without decreasing, even increasing the security performance. It is proposed to embed the payload while minimizing a suitably defined distortion function. The embedding distortion is computed as a sum of relative changes of coefficients in a cover image.