# Secure NIfTI Image Authentication Scheme for Modern Healthcare System
## 4 Proposed Watermarking Method
### Watermark Extraction Process
The PSNR evaluation formula is given in Equation (30). PSNR is affected by the Mean Square Error. \[\mathrm{SLT}\left[\mathrm{LL}^{\prime}\right]=\left[\mathrm{LH}^{\prime}, \mathrm{HL}^{\prime},\mathrm{LL}^{\prime},\mathrm{HH}^{\ast}\right]\]0

To evaluate how similar the original slice and the watermarked slice are to one another, the SSIM is used. The value of the SSIM can vary from \(-1\) to \(+1\); if SSIM is equal to \(1\), then the original slice and the watermarked slice are the same. The SSIM is computed using Equation (30)

\[\text{SSIM}(x,y)=\frac{\left( \begin{array}{c}2\mu_{x}\mu_{y}+c_{1}\end{array}  \right)\left(2\sigma_{xy}+c_{2}\right)}{\left(\mu_{x}^{2}+\mu_{y}^{2}+c_{1} \right)\left(\sigma_{x}^{2}+\sigma_{y}^{2}+c_{2}\right)} \tag{30}\]

where \(\mu_{x}\) and \(\mu_{y}\) represent the mean values of the original image and the watermarked image, respectively; \(\sigma_{x}^{2}\) and \(\sigma_{y}^{2}\) represent the variances in the original image and the watermarked image, respectively. \(\sigma_{xy}\) is the covariance. Estimating the degree of similarity between the host slice and the generated watermarked slice is necessary to evaluate how resistant the proposed method is. This is performed with the help of the NC parameter. If the NC value is quite near to one, the solution provided is effective in terms of recovery strength. NC computation is given as Equation (31). \[\text{NC}=\frac{\sum_{x=1}^{M}\sum_{y=1}^{N}w(x,y)\times w*(x,y)}{\sum_{x=1}^{ M}\sum_{y=1}^{N}w^{2}(x,y)} \tag{31}\]

Figure 5: All slices in one NIfTI image. The following is a definition of the universal image quality index Q:

\[\text{Q}=\frac{4\sigma_{xy}\overline{x}\,\overline{y}}{\left(\sigma_{x}^{2}+ \sigma_{y}^{2}\right)\left[\left(\overline{x}\right)^{2}+\left(\overline{y} \right)^{2}\right]} \tag{32}\]

### Result Analysis

Experiments were carried out to investigate the fundamental prerequisites of the proposed watermarking scheme: visual quality of watermarked image, security, integrity, confidentiality, invisibility, and robustness. The ability to hide the watermark in an image without affecting its visual quality is referred to as invisibility. PSNR is a critical statistic for determining invisibility. The performance of the proposed approach is tested on 10 diverse NIfTI images, and the slices used for the watermark insertion and extraction process are Slc1 to Slc10. The results showed that our approach was imperceptible and resilient. The pixel size of the slices is 630 \(\times\) 630 pixels, while the watermark size is set at 128 \(\times\) 128 pixels, as shown in Figure 6.

Our approach's performance was evaluated using a selected slice of the NIfTI images. Table 1 displays the image quality evaluation parameters of the watermarking system as well as the extracted watermark. If Q, NC, and SSIM are close to one, this signifies that the original and watermarked slices are essentially identical. The slice that is watermarked has a PSNR that is higher than 53 dB, indicating that the watermarked image is of exceptionally high quality. The extracted watermark quality from all the slices is significant, proving that our proposed scheme is suited for the watermarking of NIfTI images. Figure 6: Slices of NIfTI image (Slc1 to Slc10) used for experimental analysis.