Secure and invisible data hiding in 2-color images

In an earlier paper, we propose a steganography scheme for hiding a piece of critical information in a host binary image. That scheme ensures that in each m×n image block of the host image, as many as [log₂(mn+1)] bits can be hidden in the block by changing at most 2 bits in the block. As a sequel of that work, in this paper we propose a revised scheme that can maintain higher quality of the host image by sacrificing some data hiding space. The new scheme can still offer a good data hiding ratio. It ensures that for any bit that is modified in the host image, the bit is adjacent to another bit which has a value equal to the former´s new value. Thus, the hiding effect is quite invisible