Hierarchical High Capacity Data Hiding in JPEG Crypto-compressed Images

International audience; With the fast development of cloud computing, exchanging JPEG compressed images in a secure way has significantly increased. Data hiding in encrypted images (DHEI) is an effective way to embed additional data directly into the encrypted domain. In recent state-of-the-art methods, almost all DHEI processes focused on uncompressed images. Recently, some schemes using data hiding (DH) in JPEG crypto-compressed images have been designed, but most of them are not fully JPEG format compliant. In this paper, we propose a hierarchical high capacity data hiding (HHCDH) approach for JPEG cryptocompressed images. After encrypting every non-null coefficients, they are processed from low to high frequencies. Sign bits that are specific to them are then substituted by bits of a secret message. During the decoding phase, correlations between neighboring blocks are exploited to hierarchically recover the original sign bit values. According to our experiments, we achieve to obtain a high payload value, while preserving a very good quality of the reconstructed JPEG image. Index Terms-Signal processing in the encrypted domain, data hiding, crypto-compression, JPEG compression.