An Empirical Study of Steganography and Steganalysis of Color Images in the JPEG Domain

摘要

This paper tackles the problem of JPEG steganography and steganalysis for color images, a problem that has rarely been studied so far and which deserves more attention. After focusing on the 4:4:4 sampling strategy, we propose to modify for each channel the embedding rate of J-UNIWARD and UERD steganographic schemes in order to arbitrary spread the payload between the luminance and the chrominance components while keeping a constant message size for the different strategies. We also compare our spreading payload strategy w.r.t. two strategies: (i) the concatenation of the cost map (CONC) or (ii) equal embedding rates (EER) among channels. We then select good candidates within the feature sets designed either for JPEG or color steganography. Our conclusions are threefold: (i) the GFR or DCTR features sets, concatenated on the three channels offer better performance than ColorSRMQ1 for JPEG Quality Factor (QF) of 75 and 95 but ColorSRMQ1 is more sensitive for QF = 100, (ii) the CONC or EER strategies are suboptimal, and (iii) depending of the quality factors and the embedding schemes, the empirical security is maximized when between 33% (QF = 100, UERD) and 95% (QF = 75, J-UNIWARD) of the payload is allocated to the luminance channel.