A high-capacity coverless image steganography approach using block-level hash encoding and sequence category mapping: WYSAWIS

A high-capacity coverless image steganography approach using block-level hash encoding and sequence category mapping: WYSAWIS

연구 분야: Strategies

학회: Multimedia Tools and Applications

Existing approaches that map multiple hash sequences to a single cover element typically use an entire image as the cover. As a result, each image can represent only one hash sequence at a time, leading to the need for transmitting a large number of cover images during the hiding process. Although an image can technically represent multiple hash sequences, its effective capacity is limited to the length L of a single sequence. Conversely, methods that use image blocks as cover elements rely on one-to-one mapping between sequences and blocks, causing the number of required blocks to grow exponentially with the sequence length. Moreover, they lack a secure and well-defined method for transmitting the location information required for message extraction. This paper proposes a novel approach that combines block-level hash encoding with sequence category mapping. By categorizing sequences and mapping a sequence category to a single image block, the method increases the effective capacity of an image, allowing a single image to convey a full message. Additionally, the number of required cover blocks reduces from to . The secure and practical transmission of location information is ensured using a distributed data hiding technique in a single cloud environment. Our method, dubbed WYSAWIS (What You See And What It iS), highlights how seemingly innocuous image and file transfers may hide data. Compared to other coverless image steganography approaches, WYSAWIS allows grouping up to 6,435 sequences under one cover block, which reduces the number of cover blocks from 32,768 to just 16.