Coverless Image Steganography Framework with Increased Payload Capacity

This paper proposes a coverless image steganog- raphy framework with increased payload hiding capacity for confidential information transmission. This is superior to existing coverless schemes which require transmitting a stream of stego images in sequence due to the issue of small hiding capacity per stego image. In addition, by directly linking the secret with existing or generated images, coverless schemes are proven to be more secure as compared to traditional image steganography which embeds confidential message by modifying pixel values of a given image (known as cover). Specifically, we build a dictionary- based encoding scheme using images of the MNIST handwritten digit dataset to generate the stego image. In this dataset, thousands of images carry the same digit but have variance in their shapes and pixel depth. Thus it serves as a good codebook to represent information. The proposed coverless steganography scheme holds necessary resistance to image processing operations like JPEG compression, image binarization, image scaling and image noise, i.e., the hidden message can be successfully decoded from the processed stego images.