Steganography with two JPEGs of the same scene

It is widely recognized that incorporating side-information at the sender can significantly improve steganographic security in practice. Currently, most side-informed schemes for digital images utilize a high quality “precover” image that is subsequently processed and then jointly quantized and embedded with a secret. In this paper, we investigate an alternative form of side-information in the form of two JPEG images of the same scene. The second JPEG image is used to determine the preferred polarity of embedding changes and to modulate their costs. Tests on real imagery show a very significant improvement in empirical security with respect to steganography utilizing a single JPEG image.