Steganalysis in the Presence of Watermarked Images

Watermarked images are increasingly prevalent in the internet. Hence, any practical steganalyzer has to take the presence of watermarked images into account, particularly as potential source of false alarms due to similar embedding algorithms. In this study, we investigate the impact of watermarked images on the performance of a standard steganalyzer using two recent watermarking schemes: JPEG Compression Resistance Watermarking (JCRW) in the DCT domain [1] and Controllable Secure Watermarking (CSW) [2] in the pixel domain. Our findings show that JCRW and CSW do interfere with steganalysis. In particular, CSW-watermarked images were mostly classified as stego images thus rendering the investigated steganalyzer useless because of the excessively high false alarm rate. We propose a two-step classifier to handle this problem which achieves the same performance as the original steganalyzer, but in the presence of watermarking.