# A Novel Adaptive Image Data Hiding and Encryption Scheme Using Constructive Image Abstraction
## 3 Experimental Results and Analysis
### A Comparison with the Latest Related Works  
In Table 9, we compare our algorithm with other approaches that currently represent the forefront of research in adaptive data hiding for HDR images. Our scheme is the only algorithm that can support the image abstraction. In addition, while [11; 12; 13; 15] concealed secret messages by modifying the existing cover images, our scheme and that in [14] adopted constructive data hiding, where secret messages are embedded by constructing a stego image directly. Our scheme and that in [14] can support image encryption to further protect the hidden messages.  
In terms of the embedding rate, it ranges from 0.5 to 20.0 bpp, with most competitors being outperformed by our algorithm, except for that in [15] since the encoding bit length in an HDR RGBE is 32, while that in HDR OpenEXR is 48. In addition, the space to conceal secret message in RGBE is far less than that in OpenEXR, since the Exponential channel is required to be intact for message concealment in order to avoid significant pixel distortion.  
Our algorithm generates a moderate level of image quality, where a tone-mapped stego image has the PSNR of 50.949 dB, lower than [15] but close to [13; 14]. It is worth noting the PSNR is influenced by tone-mapping algorithms as well as the number of hidden secret messages. Our algorithm offers a larger embedding rate than most competitive schemes, while still producing the stego image with good quality exhibiting moderate PSNR values and high SSIM values. We conclude that our approach surpasses the current state-of-the-art methods.  
Table 10, presents a comparison between our proposed encryption scheme and state-of-the-art algorithms for HDR images. Upon closer examination, these schemes did not undergo a thorough security analysis. In contrast, our proposed scheme has conducted a comprehensive security evaluation process, consisting of seven different metrics. Undoubtedly, security is the most crucial aspect of an encryption algorithm. The lack of comprehensive security analysis leaves room for doubt that the ciphered images can effectively withstand malicious attacks, such as differential and statistical attacks [34; 35].  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Scheme** & **Proposed** & [14] & [13] & [15] & [12] & [11] \\ \hline
**Year** & 2023 & 2022 & 2020 & 2017 & 2011 & 2009 \\
**Input Image** & RGBE/LDR & OpenEXR & RGBE & OpenEXR & RGBE & RGBE \\
**Image** & **Yes** & No & No & No & No & No \\
**Abstraction** & **Yes** & **Yes** & No & No & No & No \\
**Constructive** & **Yes** & **Yes** & No & No & No & No \\
**Encryption** & **Yes** & **Yes** & No & No & No & No \\
**ER (bpp)** & 8.332–12.428 & 7.30–9.29 & 0.490–2.292 & 2.433–20.002 & 0.1256–0.1281 & 5.04–9.70 \\
**PSNR (dB)** & 37.400–50.949 & 32.60–51.90 & 50.65–51.77 & 45.12–82.32 & N.A. & 30.00–40.00 \\
**SSIM** & 0.9693–0.9999 & 0.994–1.000 & 0.854–0.995 & 0.7572–0.9999 & N.A. & N.A. \\ \hline \hline \end{tabular}
\end{table}
Table 9: An evaluation of adaptive data hiding in comparison with state-of-the-art methods.