Abstract: A novel multi-class steganalyzer with recompression detection for JPEG images is proposed to identify steganographic methods from singly and doubly compressed stego images. Based on the statistical distribution of the first digits of DCT coefficients, a JPEG recompression detection method is proposed. Features for blind detection are extracted from the histogram, intrablock correlation, interblock correlation and spatial blockiness. Finally, a multi-class detector against current steganographic methods is constructed with support vector machine. The experimental results show that the proposed recompression detection scheme outperforms the existing methods significantly, and is robust to embedding changes. The low dimensional
steganalytic features have better performance, and the multi-class steganalyzer can identify the current JPEG steganographic methods reliably.

Key words: JPEG image, universal steganalysis, recompression detection, multi-class detection