A simple data hiding technique for binary images is proposed. The proposed method embeds secure data at the edge portion of host binary image. We find the best changeable pixels in a block by changing distance matrix dynamically and compute its changeable score by weighting mechanism. The proposed method uses the pseudo random number generator based on Rabin Public Key Cryptography System to embed secret data into a binary image. According to the pseudo random number generator, we can distribute secret data into the binary image to make binary image quality better and get high security.