# Separable Data-Hiding Scheme for Encrypted Image to Protect Privacy of User in Cloud
## 4 Experiments
### Performance Analysis against Data-Loss  
In the experiment in Section 4.1, we assumed that there was no distortion of the stego-image during transmission and storage, but that does not represent reality. Let us assume that the simulation experiments were performed in an ordinary communication environment with binary pulse amplitude modulation (BPAM) baseband signals and controllable additive white Gaussian noise (AWGN) [31]. The transmission characteristic of this system [31] with the bit-error rate (BER) versus the signal-to-noise ratio (SNR) is shown in Figure 9, where \(E_{b}\) is energy per bit and \(N_{0}\) is the spectral density of the noise. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **[PERSON] et al.’s Scheme [24]** & **[PERSON] et al.’s Scheme [25]** & **Our Proposed Scheme** \\ \hline Compression ratio \(\beta\) & 0.8 & 0.8 & 0.8 \\ \hline The embedding capacity & 65,536 bits & 131,072 bits & 208,896 bits \\ \hline Size of stego-image & 512 \(\times\) 408 & 512 \(\times\) 512 & 512 \(\times\) 408 \\ \hline Quality of the recovered image & & & \\ before extracting the hidden data & 26.9 dB & 37.98 dB & 36.04 dB \\ \hline Quality of the recovered image after & & & \\ extracting the hidden data & 40.8 dB & 45.75 dB & - \\ \hline If the compression causes distortion & & & \\ of the hidden data & Yes & Yes & No \\ \hline The complexity of extraction process & Hard & Hard & Easy \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparisons of other relevant schemes and our proposed scheme. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Block Size**} & \multicolumn{5}{c}{**Compression Ratio \(\beta\)**} \\ \cline{2-7}  & **0.9** & **0.8** & **0.6** & **0.5** & **0.25** \\ \hline \multirow{3}{*}{\(8\times 8\)} & PSNR & 36.56 & 35.94 & 34.74 & 33.79 & 31.25 \\  & SSIM & 0.9757 & 0.9738 & 0.9655 & 0.9590 & 0.9353 \\  & EC & 237,568 & 208,896 & 155,648 & 131,072 & 65,536 \\ \hline \multirow{3}{*}{\(16\times 16\)} & PSNR & 35.81 & 35.47 & 34.56 & 33.78 & 30.93 \\  & SSIM & 0.9712 & 0.9697 & 0.9632 & 0.9580 & 0.9267 \\  & EC & 235,520 & 209,920 & 157,696 & 131,072 & 65,536 \\ \hline \multirow{3}{*}{\(32\times 32\)} & PSNR & 35.75 & 35.19 & 34.42 & 33.79 & 31.35 \\  & SSIM & 0.9708 & 0.9653 & 0.9600 & 0.9546 & 0.9272 \\ \cline{1-1}  & EC & 236,032 & 209,664 & 157,184 & 131,072 & 65,536 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: PSNR (dB) and EC (bits) with different compression ratios and block sizes for Lena. The stego-images in our experiment were transmitted in an ordinary communication environment, and controlled AWGN was added in the channel. We used the stego-images that were received to recover the protected images and extract the hidden images that corresponded to each BER, and the results are shown in Figure 10. Here, the compression ratio was 0.25 and the size of the block was 8. Figure 10 clearly shows that a poor transmission environment has more influence on the quality of the recovered images than it has on the quality of the extracted images. In Figure 10b, when BER was 6 \(\times\) 10\({}^{-2}\), the fingerprint pattern of the extracted image clearly was discernible despite the presence of noise around them. But the PSNR of the recovered image was only 12.26 dB, which is hardly acceptable to the human eye. However, when the BER was lower, both the extracted image and the recovered image had good visual qualities. We also conducted a group of cropping tests, and the results are shown in Figure 11. To illustrate the cropping ratio more visually, cropped parts of the images are shown with black pixels. Obviously, when the stego-image was cut in half, i.e., the cropping ratio was 50% in Figure 11a, the visual effect of the extracted image was diminished by noise, but the fingerprint pattern was still discernible, and the quality of the recovered image was satisfactory. As the cropping ratio decreased, the quality of the extracted and recovered images increased.