One-third probability embedding: a new ±1 histogram compensating image least significant bit steganography scheme

A new method is introduced for the least significant bit (LSB) image steganography in spatial domain providing the capacity of one bit per pixel. Compared to the recently proposed image steganography techniques, the new method called one-third LSB embedding reduces the probability of change per pixel to one-third without sacrificing the embedding capacity. This improvement results in a better imperceptibility and also higher robustness against well-known LSB detectors. Bits of the message are carried using a function of three adjacent cover pixels. It is shown that no significant improvement is achieved by increasing the length of the pixel sequence employed. A closed-form expression for the probability of change per pixel in terms of the number of pixels used in the pixel groups has been derived. Another advantage of the proposed algorithm is to compensate, as much as possible, for any changes in the image histogram. It has been demonstrated that one-third probability embedding outperforms histogram compensating version of the LSB matching in terms of keeping the image histogram unchanged.