## 5 Experimentation and Performance Evaluation of Obfuscation Methods
### Performance Comparison
Therefore, in terms of space occupancy, while obfuscation methods may introduce changes, the overall impact is generally less than 10%. This slight additional space overhead is considered entirely acceptable to ensure the security and stability of the RTL code. As observed in Figure 6(b), concerning code obfuscation coverage, the analysis of RTL code by VCS is easily affected by macro-defined parameters, which leads to part of the code being overlooked and not obfuscated. In contrast, obfuscation tools exhibit higher and more stable obfuscation rates than VCS tools. This superiority is attributed to the obfuscation tools' capability to comprehensively analyze the code, ensuring a more thorough obfuscation coverage. In the comparison of obfuscation time, as illustrated in Figure 6(c), VCS completes the obfuscation in less than 1 s. In contrast, the obfuscation tool requires time for analyzing the XML syntax tree, refactoring the code, and using multiple obfuscation methods, resulting in a noticeable gap in runtime compared to VCS. Despite the longer runtime of the obfuscation tool, the protection measures are more varied and stringent. For the complexity and security of the obfuscation tool, a runtime of a few seconds is still perfectly reasonable. Several tests confirm that the proposed obfuscation methods effectively secure RTL code while preserving its correctness. Compared with other obfuscation tools, the proposed methods are able to perform multiple complex obfuscation operations with low \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Methods of Obfuscation Not Used** & **MCPU** & **DUSB** & **DAHB64** & **ALTOR** \\ \hline None * & 100.0\% & 100.0\% & 100.0\% & 98.4\% \\ Layout obfuscation & 20.4\% & 28.5\% & 34.8\% & 32.7\% \\ Parameter obfuscation & 97.0\% & 96.7\% & 98.6\% & 96.3\% \\ Critical path obfuscation & 100.0\% & 100.0\% & 100.0\% & 98.4\% \\ Code increment obfuscation & 100.0\% & 100.0\% & 100.0\% & 98.4\% \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The obfuscation rate without using a certain obfuscation method. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Obfuscation Methods** & **High Obfuscation** & **Primary Data** & **Reduce Circuit** & **Change in Space** & **Circuit Overhead** \\  & **Coverage** & **Loss** & **Performance** & **Occupancy** & **Circuit Overhead** \\ \hline Layout obfuscation & \(\surd\) & \(\surd\) & & Decrease & No effect \\ Parameter obfuscation & & \(\surd\) & & Increase & No effect \\ Critical path obfuscation & & & \(\surd\) & Increase & Increase \\ Code increment obfuscation & & & & Increase & No effect \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Characteristics of code obfuscation methods. overheads, although they do not have advantages in terms of space occupancy and obfuscation time. In inter-method comparisons, the obfuscation methods in this paper exhibit greater diversity, showcasing enhanced code protection abilities and heightened practical application potential. Figure 7: Comparison between VCS tool and obfuscation tool in this article. (**a**) Comparison of space occupancy before and after obfuscation; (**b**) Comparison of obfuscation coverage; (**c**) Obfuscation time comparison.