A high capacity reversible watermarking approach for authenticating images: Exploiting down-sampling, histogram processing, and block selection

• A high capacity reversible watermarking approach for authenticating images.
• The novel technique uses histogram processing and block selection.
• Enhanced block skipping approach ensures the correct message bit embedding.
• The idea of down-sampling; employed in a new way, improves the tradeoff.
• The location map is also used for authentication besides helping in reversibility.

Amongst the various data hiding schemes, lossless data hiding has achieved substantial attention in the recent years. Lossless watermarking also known as reversible watermarking, not only ensures the extraction of the hidden information, called watermark, but also the complete recovery of the original image as well. Recently, several interesting reversible block-based watermarking approaches using histogram processing have been reported. These approaches offer substantial watermarking capacity for a fixed image quality measure. However, there is considerable margin of improvement as regards the imperceptibility versus capacity tradeoff is concerned. Some of the watermarking applications such as those related to integrity-control need high capacity. Therefore, we present a high capacity reversible watermarking approach based on histogram processing and block selection (RW-HPBS). The proposed RW-HPBS approach exploits the concept of down sampling for effectively increasing the capacity and is useful for integrity control and authentication related applications. Two down-sampled versions, the reference and the data hiding, are obtained to create space for embedding. Authentication property is achieved by taking a secondary advantage of the location map before being compressed and embedded as an auxiliary information. The effectiveness of the proposed method is shown through comparison with the existing techniques. Experimental results show that the proposed RW-HPBS approach provides better imperceptibility versus capacity tradeoff and can detect tampering and collage attack.