# SC-SA: Byte-Oriented Lightweight Stream Ciphers Based on S-Box Substitution
## 4 Performance  
RC4 is also a software-oriented stream cipher algorithm, consisting mainly of two components, S and K, which are generally composed of two 256-byte arrays. K serves as the key input for RC4 and is used to initialize S. If K is set to 80 bits, it will decrease the security of the RC4 cipher. To ensure the minimum security threshold for RC4, S and K should be of the same size. In the performance comparison below, both K and S in RC4 are 256 bytes. Snow3G [26] is a stream cipher algorithm used in 4G mobile communication standards to protect data privacy and security in mobile communication. It is part of the 3 GPP standard and is used in 3G and 4G communication standards, making it an important encryption algorithm in the field of mobile communication. Snow3G is used to generate a key stream, which is then XORed with plaintext data to achieve encryption. The key stream is a pseudo-random number sequence generated based on an initialization vector (IV) and \begin{table}
\begin{tabular}{c c c} \hline \hline
**Data Category** & **Sample Size/Sequence Length** &
\begin{tabular}{c} **The Maximum Number of** \\ **Rejections** \\ \end{tabular} \\ \hline
80-Bit Key Avalanche & 6400/1,048,576 & 87.86 \\ Random Plaintext and & 128/1,048,576 & 4.65 \\ Random 80-Bit Keys & 3240/1,048,576 & 49.38 \\ High-Density 80-Bit Keys & 3240/1,048,576 & 49.38 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Randomness testing parameters. a key, both filled in by the user, with both being 128 bits (16 bytes) in length. Therefore, Snow3G theoretically provides 128-bit security protection. ZUC [27] is also a stream cipher algorithm primarily used in the field of mobile communication, especially in China's 3G and 4G mobile communication standards. ZUC was originally designed for China's mobile communication standards but was also submitted to the International Telecommunication Union (ITU) for global use. This makes it an international encryption algorithm and it has been applied in some international mobile communication standards. Similar to Snow3G, ZUC is used to generate a key stream for encrypting and decrypting data. The generation of the key stream depends on an initialization vector (IV) and a key. Similar to Snow3G, the ZUC algorithm is 128 bits (16 bytes), and the initialization vector (IV) length is generally 64 bits (8 bytes). Therefore, ZUC can provide 128 bits of security protection regarding key length. RC4, as a previously widely used encryption algorithm, has good performance on different platforms. Due to issues such as weak keys, some cryptographic algorithms have enhanced it, such as RC4 + [24] and other variant RC [28] algorithms. These stream ciphers mentioned above, which are international protocol standards, are compared in terms of algorithm implementation in Figure 9. The memory usage of RC4 variant algorithms does not significantly differ from that of RC4 algorithms. Like the other three algorithms, SC-SA also uses an S-box as the nonlinear component of the cipher algorithm. Both SC-SA and RC4 use an 8-bit substitution S-box, while the other two cipher algorithms employ two or more S-boxes. This results in significantly higher memory usage compared to SC-SA. The performance of these six cryptographic algorithms was tested on different computing platforms. On the \(\times\)86 platform, the Intel i5-12500H (Intel, made in China) was used, while the Qualcomm Snapdragon 410--which consists of four A53 cores--was used on the ARM platform, better representing IoT devices. The experimental results based on different platforms are shown in Figures 10-13. In the line charts, the x-axis represents the size of the encrypted data and the y-axis represents the time required to encrypt data of that size. Different platforms have different impacts on cryptographic algorithms. Snow3G does not have an implementation advantage under software conditions, whether on the \(\times\)86 platform or the ARM platform.