A Study on Visual Attack to BPCS-Steganography and Countermeasure

This paper discusses a visual attack to BPCS-Steganography (Bit-Plane Complexity Segmentation-Steganography) and presents a countermeasure. BPCS replaces noisy blocks with the binary patterns mapped from secret data. The logical operation called conjugate operation is applied to those if the binary patterns are simple. We need to keep the flag called a conjugation flag representing whether such conjugation had been applied to them. In the case where the conjugation flags must be embedded within cover images, the flags must be embedded into a fixed area. To this effect it is easy to recognize unnatural patterns on the LSB plane of stego-images. We propose a secure BPCS which is robust against the visual attack. It is realized by assigning the meaning of the conjugation flag to a pixel of each block and making the specific rule to embed and extract it.