## 4 Experimental Results and Discussion
In addition, if the image is restored, it shows the advantage of being able to restore the original cover image. When implementing [PERSON] et al. 's method [22], it is necessary to record some auxiliary information and embed it into the bitmap of the first several triples by sacrificing some embedding space. Thus, their scheme does not fully excavate and make full use of the characteristic of the AMBTC compression codes. In [PERSON] et al's method [23], each block records a pair of peak and zero points. Since the histogram modification method proposed here was first devised for gray images, it does not provide a sufficient amount of redundant bits for data hiding the compressed images, so the data hiding capacity is relatively small. [PERSON] et al. 's method [24] considers the natural correlation of quantization levels within a block and had an improved embedding capacity compared to the [PERSON] et al. 's scheme. The method we proposed is a method that can modify 1 pixel for each block and hide 4 bits, and is an optimized method to ensure data hiding efficiency and \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline \multirow{2}{*}{**Images**} & \multicolumn{2}{c}{**_T = 5_**} & \multicolumn{2}{c}{_T = 10_} & \multicolumn{2}{c}{_T = 15_} & \multicolumn{2}{c}{_T = 20_} \\ \cline{2-9}  & **EC (Bits)** & **PSNR** & **EC (Bits)** & **PSNR** & **EC (Bits)** & **PSNR** & **EC (Bits)** & **PSNR** \\ \hline Baboon & 1113 & 26.9757 & 10121 & 26.9571 & 18,649 & 26.9161 & 24,557 & 26.8607 \\ Barbara & 14,889 & 27.0702 & 26,493 & 27.0485 & 32,125 & 27.0208 & 35,153 & 26.9922 \\ Boat & 28,217 & 31.5444 & 36,133 & 31.5034 & 42,313 & 31.4161 & 47,357 & 31.2857 \\ Goldhill & 9385 & 32.8207 & 27,769 & 32.6851 & 41,445 & 32.4429 & 48,965 & 32.1992 \\ Airplane & 34,549 & 32.0017 & 44,637 & 31.9485 & 49,469 & 31.8705 & 52,657 & 31.7764 \\ Lena & 29,677 & 33.599 & 44,217 & 33.4861 & 50,637 & 33.3503 & 54,329 & 33.2079 \\ Pepper & 21,149 & 34.0397 & 45,997 & 33.8319 & 52,921 & 33.6764 & 56,149 & 33.5425 \\ Tiffany & 29,381 & 35.5651 & 45,457 & 35.3734 & 52,609 & 35.1416 & 56,497 & 34.9002 \\ Zelda & 23,301 & 36.5378 & 49,093 & 36.1607 & 55,857 & 35.9139 & 59,365 & 35.6629 \\ Average & 21,295 & 32.2393 & 36,657 & 32.1105 & 44,002 & 31.9720 & 48,336 & 29.0427 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of EC and PSNR performance according to the difference between the two quantization levels. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Images**} & \multicolumn{2}{c}{**Cover Images**} & \multicolumn{2}{c}{**[PERSON] et al.’s [22]**} & \multicolumn{2}{c}{**Proposed Method**} \\ \cline{2-7}  & **PSNR** & **Payload** & **PSNR\({}^{1}\)** & **PSNR\({}^{2}\)** & **Payload** & **PSNR\({}^{1}\)** & **PSNR\({}^{2}\)** \\ \hline Baboon & 26.9765 & 141 & 23.66 & \(+\infty\) & 1113 & 26.9757 & \(+\infty\) \\ Boat & 31.57 & 554 & 30.32 & \(+\infty\) & 28,217 & 31.5444 & \(+\infty\) \\ Airplane & 32.0372 & 1458 & 30.40 & \(+\infty\) & 34,549 & 32.0017 & \(+\infty\) \\ Lena & 33.6556 & 1213 & 33.00 & \(+\infty\) & 29,677 & 33.5990 & \(+\infty\) \\ Tiffany & 35.6576 & 1687 & 29.81 & \(+\infty\) & 29,381 & 35.5651 & \(+\infty\) \\ Average & 31.9793 & 1010 & 27.93 & \(+\infty\) & 24,587 & 31.9371 & \(+\infty\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the performance between [PERSON] et al.’s method and the proposed method. a high image quality. As shown in Table 4, it can be seen that the EC of our proposed method has the best performance. Figure 6 shows the results of decryption after hiding data in the encrypted image when the difference between the two quantization levels is \(T=5\). The quality of the decoded image including the data can be visually compared to the original. When looking at Figure 6a,b, which are the decoded images, the PSNR is clearly not high below 30 dB, which shows the image quality. Since the original image of (a) and (b) was also less than 30 dB, the PSNR of the decoded image was measured to be less than 30 dB.