An attack to BPCS-steganography using complexity histogram and countermeasure

This paper discusses an attack to BPCS-Steganography (Bit-Plane Complexity Segmentation-Steganography) and presents a countermeasure. BPCS is an image-based steganographic method. BPCS embeds secret data by replacing blocks that appear noise-like on bit-planes. Blocks on bit-planes are categorized as a "noise-like region" or an "informative region" by means of the binary-image feature called complexity. When the complexity distribution of noise-like blocks is different from the complexity distribution of the secret data that replaces those blocks, we can see an unusual shape in the form of a valley in the complexity histogram that represents the relative frequency of occurrence of the various complexities. This would be a signature of BPCS. Because steganography must hide the existence of the secret message, the signature should be removed from steganographic images. We present a method for making embedded binary patterns that quasipreserves the complexity distribution.