# [PERSON] Coding-Based Medical Image Data Hiding Method against Salt and Pepper Noise
## 5 Conclusions  
In this study, a new data hiding method based on Reed Solomon error control coding is proposed for medical images. The proposed method was tested with several medical images. Image quality results of the same type of medical images are almost the same. Stego images of the proposed method give remarkably better results compared to existing medical data hiding methods in terms of PSNR and SSIM for similar capacities. On the other hand, the secret message extracting the performance of the proposed method is compared with the results of a second method, which does not contain the proposed RS block. Salt and pepper noises of different densities were added to stego images, and the state of the retrieval of the secret message was examined. The proposed RS-based method is almost error-free, even at 10% density noise, and BER values are also almost 0. At 20% noise density, the proposed method reduces BER by 70% and increases SSIM by 30%. Hence, the RS-based data hiding shows a superior performance compared to the direct hiding algorithm up to an amount of noise density. Moreover, the proposed method tested against low density of other noises. The RS-based method reduce BER by about 70% for Gaussian and uniform noises, when speckle noised applied stego images BER reduced 27% for CT and 10% for MRI. Unfortunately, the proposed method was not reduced the BER values for speckle noise corrupted US and X-ray stego images. When the noise rate increases too much, it is no longer possible to obtain correct symbols in some codewords, because the entire codeword is broken. The performance results of the extracted secret message were compared to  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Noise Density**} & \multicolumn{2}{c}{**Proposed RS-Based**} & \multicolumn{2}{c}{[14]} & \multicolumn{2}{c}{[30]} \\ \cline{2-7}  & **BER (\%)** & **SSIM** & **BER (\%)** & **SSIM** & **BER (\%)** & **SSIM** \\ \hline
1\% & 0 & 1 & 0.15 & 0.9127 & 0.14 & n/a \\
5\% & 0.1 & 0.9811 & 1.06 & 0.9069 & 0.48 & n/a \\
10\% & 0.6 & 0.9033 & 2.47 & 0.9002 & n/a & n/a \\
20\% & 4.1 & 0.7033 & 5.77 & 0.8875 & n/a & n/a \\
50\% & 26 & 0.3144 & 21.6 & 0.8368 & n/a & n/a \\ \hline \hline \end{tabular}
\end{table}
Table 8: Comparison of BER (%) value of the secret message with existing methods (n/a: not available).  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Noise Type**} & \multirow{2}{*}{**Variance**} & \multicolumn{3}{c}{**Proposed RS-Based Method**} & \multicolumn{3}{c}{**No-RS Method**} \\ \cline{3-10}  & & **CT** & **MRI** & **US** & **X-ray** & **CT** & **MRI** & **US** & **X-ray** \\ \hline \multirow{3}{*}{Gaussian} & 0.005 & 0.9 & 0.8 & 1.1 & 1 & 5.4 & 6 & 6 & 6.4 \\  & 0.01 & 1.7 & 1.7 & 2.2 & 2.1 & 7.5 & 7.3 & 8.3 & 8.2 \\ \multirow{3}{*}{Speckle} & 0.005 & 6.4 & 1.3 & 32.4 & 42 & 9.1 & 5.9 & 31.3 & 43.1 \\  & 0.01 & 10.8 & 5 & 32.8 & 42.4 & 14.4 & 11.2 & 33.5 & 42.5 \\ Uniform & 0.1 & 2.5 & 2.7 & 2.5 & 2.4 & 9.9 & 9 & 9.5 & 9 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Comparison of BER (%) value of the secret message for different noise types.  
existing medical data hiding methods that tested the resistance to salt and pepper noise. Consequently, the proposed method provides very superior performance at different salt and pepper noise densities.  
Conceptualization, M.Z.K. and S.O.; methodology, M.Z.K. and S.O.; software, M.Z.K.; validation, M.Z.K. and S.O.; formal analysis, S.O.; investigation, M.Z.K.; resources, M.Z.K.; data curation, M.Z.K.; writing--original draft preparation, M.Z.K.; writing--review and editing, S.O.; visualization, M.Z.K.; supervision, S.O.; All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.