# A False Negative Study of the Steganalysis Tool Stegdetect
## 4 Results  
All the results were analysed and interpreted in different phases deepening on the image dataset. Phase one analysed a total of 500 images manipulated by seam-carve from SAM Houston university image database, both at 75 quality before embedding using jphide with randomly generated bits. The table below gives a summary of the overall detection during the analysis. We noted that detection of jphide method in the images was based on the changes in the sensitivity values. However, other algorithms detected by the tool are the circumstances in which stegdetect during the analysis identified other steganographic methods which during the embedding process we did not use. Table 1 shows that the highest ratio of detection with sensitivity results is 67.13% of the manipulated images by seam-carve which considering the level of the ratio is very high. Meanwhile, detection results for jphide were very low. Figure 1: Sample results of the jphide method. All results for false negative, jphide and other algorithm keep changing with change in sensitivity as shown in Table 2. The beginning of the analysis with low sensitivity value (0.1) the false negative ratio was very high (98%). However, a systematic drop was realised in the false negative ratio between sensitivity values 0.1 and 0.7, furthermore, the false negative ratio with sensitivity values 5.2-10.0 had a drastic drop as shown in Table 2 below. Here it becomes clear that the tool became more effective in detecting steganographic method used in embedding the secret messages. As shown in Figure 2 above, between sensitivity values 0.1 and 0.5 there were no changes in the results for jphide. Meanwhile, detection of jphide increased substantially between 0.7 and 10.0 with their related confidence levels (*, ***). Between 0.1 and 0.5 jphide (*) was stable until it got to the range 0.7-3.4 when there was fluctuation in the detection ratio, it then had a sharp increased with 5.2 sensitivity, after which it experienced another sharp decrease between (7.3 and 10.0). For jphide (**) between 1.5 and 10.0 there was a constant increase except with sensitivity of 3.4 which experience some drop. However, jphide (***) maintained the increasing of its ratio. \begin{table}
\begin{tabular}{l l l l l l l} \hline
**Sensitivity** & **False Negative** & **Likely False** & **jphide(*)** & **jphide(**)** & **jphide(***)** & **OTHER** \\
**Value** & & & **Positive (Skipped)** & & & **-ALG** \\ \hline
0.1 & 98.00\% & 2.00\% & 0.00\% & 0.00\% & 0.00\% & 0.00\% \\
0.3 & 97.80\% & 2.00\% & 0.00\% & 0.00\% & 0.00\% & 0.20\% \\
0.5 & 97.80\% & 2.00\% & 0.00\% & 0.00\% & 0.00\% & 0.20\% \\
0.7 & 96.40\% & 2.00\% & 1.40\% & 0.00\% & 0.00\% & 0.20\% \\
1.5 & 89.40\% & 2.00\% & 6.20\% & 2.00\% & 0.00\% & 0.40\% \\
3.4 & 87.20\% & 2.00\% & 2.20\% & 0.00\% & 8.20\% & 0.40\% \\
5.2 & 17.60\% & 2.00\% & 69.60\% & 2.20\% & 8.20\% & 0.40\% \\
7.3 & 11.40\% & 2.00\% & 17.40\% & 59.00\% & 9.30\% & 0.40\% \\
10.0 & 8.60\% & 2.00\% & 9.40\% & 69.20\% & 10.40\% & 0.40\% \\ \hline \end{tabular}
\end{table} 
Table 2: Results from manipulated images by seam-carve based on sensitivity values. \begin{table}
\begin{tabular}{l l l l l l l} \hline
**Sensitivity** & **False Negative** & **Likely False** & **jphide(*)** & **jphide(**)** & **jphide(***)** & **OTHER** \\
**Value** & & & **Positive (Skipped)** & & & **-ALG** \\ \hline
0.1–10.0 & 67.13\% & 2.00\% & 11.80\% & 14.71\% & 4.07\% & 0.29\% \\ \hline \end{tabular}
\end{table} 
Table 1: Rate of sensitivity results from 500 images manipulated by seam-carve. Figure 2: Changes in the jphide rate with different sensitivities for seam carve manipulated images. As per the analysis above, the level of confidence in detection by stegdetect is directly proportional to the sensitivity values. Meaning, the higher the sensitivity value the higher the confidence in detecting jphide. Furthermore, the high increase of confidence in detecting jphide was between (3.4 and 10.0).