PSteg: Steganographic embedding through patching

In this paper we propose a novel approach to image steganography in which embedding is done without making explicit modifications to the image; that is, the embedding distortion introduced to the cover image is both perceptually and statistically ensured to be less detectable. If an image is divided into blocks and each block is hashed, then the hash values could represent the embedded message content. A set of replacement blocks can be obtained by consecutively capturing images of the same scene (or resampling the incident light). Since image content remains the same and noise is sampled, the set of replacements are statistically compatible while still providing unique hash values. With such an approach the embedder can choose the block with hash value corresponding to the message content without violating any of the natural image statistics. When applied to JPEG images, experiments show that this technique can achieve embedding rates of.063 bits per DCT coefficient or.157 bits per nonzero DCT coefficient while still remaining undetectable by Farid's universal steganalysis tool.