Estimating the Redundancy Factor for RA-encoded sequences and also Studying Steganalysis Performance of YASS

Our recently introduced JPEG steganographic method called Yet Another Steganographic Scheme (YASS) can resist blind steganalysis by embedding data in the discrete cosine transform (DCT) domain in randomly chosen image blocks. To maximize the embedding rate for a given image and a specified attack channel, the redundancy factor used by the repeat-accumulate (RA) code based error correction framework in YASS is optimally chosen by the encoder. An efficient method is suggested for the decoder to accurately compute this redundancy factor. We demonstrate the redundancy estimation for the quantization index modulation and matrix embedding based schemes through Sec. 2-4. The second part of this technical report (Sec. 5) discusses the steganalysis performance of YASS, using different embedding schemes, such as matrix embedding and quantization index modulation, and after using a variety of steganalysis features. Here, we shall be discussing the estimation of the RA code redundancy factor for the following 2 types of methods. For each method, the databits are RA-encoded using a suitable redundancy factor and then different embedding techniques are used to embed the code bits in the given image.