A new high capacity and secure image realization steganography based on ASCII code matching

Digital Steganography is the art of hiding secret messages behind an innocent looking digital media that do not raise suspicions. In this paper, a new proposed image realization steganography method is introduced which is a mapping-based method that hides in an unrevealed manner and without any change in the image cover file. The image cover is only used for referencing. The proposed method generates the cover-secret mapping that will realize the concealed secret message without embedding the real message. A mapping between the American Standard Code of Information Interchange (ASCII) codes of a secret message and an image is performed and the positions of the secret message in the image is noted in a position array. This reference positions are then sent to the receiver after first being compressed by Huffman algorithm and then encrypted using Advanced Encryption Standard with 128 bits key (AES-128). The position array and the cover image are transferred separately, so that the interception of any one file alone will not conceal any information. In addition, it has unlimited capacity as specific matching positions can be used more than once. Furthermore, the proposed method has a reduced size of position key and mapping table, hence having high-speed searching and matching compared to prevailing methods. Furthermore, several experimental tests have been applied to assess the efficiency and performance of the new proposed method to evaluate it according to the widely used metrics: Mean Squared Error (MSE) and Peak Signal to Noise Ratio (PSNR). From the security point of view, Structural Similarity Index Measure (SSIM) together with Histogram have been performed. Moreover, it is critiqued showing its pros and cons and further compared with existing state-of-the-art research. The experimental results verified the efficacy of the new proposed method.