Natural Steganography in JPEG Compressed Images

Tomáš Denemark (1) , Patrick Bas (2) , Jessica Fridrich (3, 1)

1 Binghamton University [SUNY]
2 CRIStAL - Centre de Recherche en Informatique, Signal et Automatique de Lille - UMR 9189
3 ECE - Department of Electrical and Computer Engineering

In natural steganography, the secret message is hidden by adding to the cover image a noise signal that mimics the het-eroscedastic noise introduced naturally during acquisition. The method requires the cover image to be available in its RAW form (the sensor capture). To bring this idea closer to a practical embedding method, in this paper we embed the message in quantized DCT coefficients of a JPEG file by adding independent realiza-tions of the heteroscedastic noise to pixels to make the embedding resemble the same cover image acquired at a larger sensor ISO setting (the so-called cover source switch). To demonstrate the feasibility and practicality of the proposed method and to validate our simplifying assumptions, we work with two digital cameras , one using a monochrome sensor and a second one equipped with a color sensor. We then explore several versions of the embedding algorithm depending on the model of the added noise in the DCT domain and the possible use of demosaicking to convert the raw image values. These experiments indicate that the demo-saicking step has a significant impact on statistical detectability for high JPEG quality factors when making independent embedding changes to DCT coefficients. Additionally, for monochrome sensors or low JPEG quality factors very large payload can be embedded with high empirical security.

Domaines: Traitement du signal et de l'image [eess.SP]

Tomáš Denemark, Patrick Bas, Jessica Fridrich. Natural Steganography in JPEG Compressed Images. Electronic Imaging, Jan 2018, San Francisco, United States. ⟨hal-01687194⟩