In this paper, we study moderately significant bit data hiding techniques for high-definition (HD) images. In contrast to least significant bit data hiding, we explore the potential of HD images to engage higher order bits for increasing the capacity of hiding secret images. In particular, the number of secret images embedded in moderately significant bits of a given cover image is successively increased to study the impact of this data hiding approach on image fidelity and image quality in the context of HD images. A comprehensive performance assessment is conducted on the stego-image carrying the secret images in terms of peak-signal-to-noise ratio (PSNR) and structural similarity (SSIM) index. It is shown that HD images indeed offer the potential of hiding several images within certain image fidelity and objective perceptual image quality constraints of the resulting stego-HD images. © 2018 IEEE.

Mobile services have seen a shift from voice services toward visual stimuli-based services ranging from mobile imaging over mobile gaming to upcoming mobile extended reality applications. In this paper, given the increased resolutions of the related mobile multimedia formats, we propose and examine positioning strategies for light-weight data hiding of secret images in moderately significant bits of high-definition (HD) cover images. Apart from linear and random positioning, visual attention mechanisms of the human visual system are addressed by separately utilizing either the background or center of the HD cover image for data hiding. A performance assessment of these positioning strategies is conducted in terms of the peak-signal-to-noise ratio (PSNR), structural similarity (SSIM) index, and visual information fidelity (VIF). It is shown that HD cover images indeed can carry more than a single secret image until noticeable quality loss is observed. Further, it is revealed that linear positioning of secret images in the whole, background, or center of HD cover images outperforms random positioning. As for the utilized performance metrics, it has been observed that PSNR cannot differentiate among the positioning strategies as it measures pixel-by-pixel differences and hence removes the impact of the position of the hidden data. As for the two quality metrics, compared to the SSIM index, VIF is found to stronger differentiate among the performance of the considered positioning strategies.

In this paper, we propose a spherical light-weight data hiding technique for 360-degree videos with equirectangular projection between sphere and plane. In particular, computationally efficient least significant bit (LSB) data hiding is applied to the color encoded equirectangular projection of the sphere. As viewers put more attention to the areas around the equator of a 360-degree video compared to the poles, LSB data hiding may be performed in the regions around the poles without causing perceptually significant quality degradation. In addition, the equirectangular projection induces a huge amount of data redundancy in the areas near the poles which increases the capacity available for LSB data hiding. A performance assessment of the proposed spherical light-weight data hiding technique is conducted using the weighted-to-spherically-uniform peak-signal-to-noise ratio (WS-PSNR) and the Craster parabolic projection PSNR (CPP-PSNR). Because both metrics take the non-linear relationship between samples on the sphere and the samples mapped to the plane into account, they are well suited for assessing the performance of the spherical LSB data hiding technique. Numerical results are provided for scenarios in which a 360-degree cover video carries a secret video using different numbers of bit planes. It is shown that video fidelity in terms of WS-PSNR and CPP-PSNR is indeed kept high in the 360-degree stego-video as long as the LSB data hiding is performed in the areas around the poles. © 2019 IEEE.

Steganography has been widely used to embed secret data in cover multimedia carriers including digital image, audio, and video files such that the confidential information being communicated is hidden. Immersive multimedia, e.g., 360° videos, have recently received increased attention as promising applications for the Internet and 5G mobile networks. In this paper, we focus on using steganography for hiding secret data in an immersive multimedia carrier. Specifically, a spherical least significant bit (LSB) data hiding approach is proposed to embed secret videos in 360° cover videos along with morphological operations. Due to viewers are paying less attention to the North and South Poles compared to the Equator region of 360° videos, LSB data hiding is performed around the poles of the equirectangular projection of the sphere to the plane. Data hiding capacity is increased by using morphological operations in the remaining mid-region around the Equator which broadens the edge area for embedding secret data. The proposed spherical LSB data hiding technique may be used to hide secret videos or other confidential data in 360° cover videos. It can also be used to increase available bandwidth for communication purposes as long as embedded data has no significant impact on the quality as perceived by the end-user. A performance assessment of the proposed approach is conducted with respect to data hiding capacity and objective perceptual video quality. Numerical results are provided for a wide range of scenarios illustrating the trade-offs between capacity and quality. © 2019 IEEE.