“Steganalysis in Technicolor” Boosting WS detection of stego images from CFA-interpolated covers

Steganographic security in empirical covers is best understood for grayscale images. However, the world, and almost all digital images of it, are more colorful. This paper extends the weighted stego-image (WS) steganalysis method to detect stego images produced from covers that exhibit traces of color filter array (CFA) interpolation, which is common for images acquired with digital cameras. The approach combines techniques of CFA forensics with state-of-the-art WS steganalysis. Empirical results from large datasets indicate significant increases in detection performance, in particular for small payloads. This specific weakness of color covers calls into question the common assumption that grayscale image steganography generalizes to color images by treating each chroma channel independently.