An Effective Maximum Distortion Controlling Technology in the Dual-Image-Based Reversible Data Hiding Scheme

The dual-image information hiding method has received considerable research attention on account of its high hiding capacity and favorable stego-image quality. The dual-image hiding technology encodes secret data across two images, requiring both stego-images to recover the correct secret data. Many factors affect the embedding capacity and image quality of the dual-image hiding method, including the nature of the hidden data, the block size, and the method by which pixels are modified. This study analyzes and encodes secret data, while controlling the degree of pixel distortion using two parameters - NC and MXD to improve the image quality. The NC parameter controls how many codes are used to re-encode a secret symbol, which is used to control the number of code combinations. MXD specifies the maximum distortion of each code combination and is used to limit image distortion. To improve the effectiveness of the encoding, a pair of digital combinations was assigned according to the frequency of the secret numeric messages. A highly uniform secret message was encoded using a small distortion code. Subsequently, the code was concealed within the cover image, generating two stego-images. The experimental results indicate that the proposed method achieved not only a better embedding rate but also a greater image quality compared with previous methods. In particular, with regard to the smooth image, the image quality of the stego-image was higher than 64.27dB when the proposed scheme was applied. Furthermore, this study utilized many steganalytic technologies to validate the security of the proposed scheme.