HiNet: Deep Image Hiding by Invertible Network

Image hiding aims to hide a secret image into a cover image in an imperceptible way, and then recover the secret image perfectly at the receiver end. Capacity, invisibility and security are three primary challenges in image hiding task. This paper proposes a novel invertible neural network (INN) based framework, HiNet, to simultaneously overcome the three challenges in image hiding. For large capacity, we propose an inverse learning mechanism by simultaneously learning the image concealing and revealing processes. Our method is able to achieve the concealing of a full-size secret image into a cover image with the same size. For high invisibility, instead of pixel domain hiding, we propose to hide the secret information in wavelet domain. Furthermore, we propose a new low-frequency wavelet loss to constrain that secret information is hidden in high-frequency wavelet subbands, which significantly improves the hiding security. Experimental results show that our HiNet significantly outperforms other state-of-the-art image hiding methods, with more than 10 dB PSNR improvement in secret image recovery on ImageNet, COCO and DIV2K datasets. Codes are available at https://github.com/TomTomTommi/HiNet.