On steganalysis of random LSB embedding in continuous-tone images

We present an LSB steganalysis technique that can detect the existence of hidden messages that are randomly embedded in the least significant bits of natural continuous-tone images. The technique is inspired by the recent work of J. Fridrich et al. (see Proc. ACM Workshop on Multimedia and Security, p.27-30, 2001) and just like their work, it can also precisely measure the length of the embedded message, even when the hidden message is very short relative to the image size. The key to our success is the formation of some subsets of pixels whose cardinalities change with LSB embedding, and such changes can be precisely quantified under the assumption that the embedded bits are randomly scattered. Interestingly, our study on steganalysis of LSB embedding sheds light on the work of Fridrich et al. on the detection of LSB embedding, and offers an analytical proof of an observation made by them.