A Steganography Scheme on JPEG Compressed Cover Image with High Embedding Capacity

Joint Photographic Experts Group (JPEG) is one of the widely used lossy image compression standard and in general JPEG based compressed version images are commonly used during transmission over the public channel like the Internet. In this paper, the authors have proposed a steganography scheme where the secret message is considered for embedding into the JPEG version of a cover image. The steganography scheme initially employs block based Discrete Cosine Transformation (DCT) followed by some suitable quantization process on the cover image to produce the transformed coefficients. The obtained coefficients are considered for embedding the secret message bits. In general, most of the earlier works hide one bit message into each selected coefficient, where hiding is carried out either directly modifying the coefficients, like employing the LSB method or indirectly modifying the magnitude of the coefficients, like flipping the sign bit of the coefficients. In the proposed scheme, instead of embedding the secret message bits directly into the coefficients, asuitable indirect approach is adopted to hide two bits of the secret message into some selected DCT coefficients. As per the conventional approach, the modified coefficients are further compressed by entropy encoding. The scheme has been tested on several standard gray scale images and the obtained experimental results show the comparative performance with some existing related works.