Capacity on Demand Steganography Through Adaptive Threshold Strategy

In the process of secret communication, in fact, the length of each transmission of ciphertext will never be the same. In order to meet dynamic length of ciphertext and provide a good image quality, a novel adaptive threshold strategy is presented. Firstly, a threshold pixel value and a k value are decided dynamically based on the length of ciphertext and the cumulative statistics of cover-image’s pixel value. Then if a pixel value is more than threshold value, more than k bits secret data can be embedded by using modified Least Significant Bit (LSB) substitution method, or the data of equal or less than k bits can be embedded. This dynamic strategy can adjust hiding capacity consistent with the length of secret message, and the secret data can be embedded in stego-image as evenly as possible. Quality of stego-image would be improved by this way. The experimental results, the proposed method not only achieves a larger embedding capacity, but also has higher visual quality of stego-image than most of proposed LSB based methods.