Image steganography using mod-4 embedding algorithm based on image contrast

In order to improve the capacity of the hidden secret data and to provide an imperceptible stego image quality, a new image steganography method based on image contrast is presented. A group of 2 × 2 blocks of non-overlapping spatially adjacent pixels is selected as the valid block for embedding the secret message. The modulo 4 arithmetic operation is further applied to all the valid blocks to embed a pair of binary bits using the shortest route modification scheme. Each secret message is also encrypted by RSA encryption algorithm to provide the system with more security. Data will be embedded inside the image using the pixels. Then the pixels of stego image can then be accessed back in order to retrieve back the hidden data inside the image. However, a secret key is needed by the receiver in order to retrieve back the data. This secret key is generated using the RSA decryption algorithm. By using the secret key to retrieve the data, it maintains privacy, confidentiality and accuracy of the data. The proposed method was tested on different gray scale images. From the experimental results, compared with the some well-known adaptive and non-adaptive steganography algorithms, the proposed method provides larger embedding capacity, while being less detectable by steganalysis methods.