# Security Issues in IoT-Based Wireless Sensor Networks: Classifications and Solutions
## 3 Security Protection Schemes
### Encryption Schemes
#### 3.1.2 Symmetric Encryption  
The authors in [58] evaluated different encryption schemes on a variety of embedded architectures, including low-, mid-, and high-end embedded processors. The measurements \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Input**} & \multirow{2}{*}{**Security**} & \multicolumn{2}{c}{**Encryption**} & \multicolumn{2}{c}{**Decryption**} & \multicolumn{2}{c}{**Total Time**} \\ \cline{3-8}  & & **ECC** & **RSA** & **ECC** & **RSA** & **ECC** & **RSA** \\  & & **Enc. Time** & **Enc. Time** & **Dec. Time** & **Dec. Time** & **Total Time** & **Total Time** \\ \hline \multirow{3}{*}{8-bit} & 80 & 0.4885 & 0.0307 & 1.3267 & 0.7543 & 1.8152 & 0.7850 \\ \cline{2-8}  & 128 & 3.8763 & 0.0305 & 1.7690 & 6.9409 & 5.6453 & 6.9714 \\ \cline{2-8}  & 144 & 4.7266 & 0.0489 & 2.0022 & 13.6472 & 6.7288 & 13.6962 \\ \hline \multirow{3}{*}{64-bit} & 80 & 2.1685 & 0.1366 & 5.9099 & 5.5372 & 8.0784 & 5.6738 \\ \cline{2-8}  & 128 & 15.0882 & 0.1672 & 7.3584 & 46.4782 & 22.4466 & 46.6454 \\ \cline{2-8}  & 144 & 20.2308 & 0.1385 & 8.4785 & 77.7642 & 28.7093 & 77.9027 \\ \hline \multirow{3}{*}{256-bit} & 80 & 7.9240 & 0.5596 & 22.8851 & 19.3177 & 30.8091 & 19.8772 \\ \cline{2-8}  & 128 & 58.4386 & 0.5611 & 27.4060 & 209.6086 & 85.8446 & 210.1697 \\ \cline{1-1} \cline{2-8}  & 144 & 77.5034 & 0.5718 & 32.1522 & 311.0649 & 109.6556 & 311.6368 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of encryption, decryption, and total execution time of ECC and RSA [56]. were performed on Atmel AVR (8-bit), Mitsubishi M16C (16-bit), and StrongARM and Xscale (32-bit) platforms. In the study, five popular encryption schemes were selected, namely RC4, RC5, IDEA, SHA-1, and MD5. Among them, RC4 and RC5 are two symmetric encryption algorithms that use the same key to perform both encryption and decryption. RC4 uses a 256-byte permutation which is generated from the input key [59]. Similarly, RC5 uses fixed data blocks 32 to 128 bits in length. RC5 allows the use of keys 0 to 2048 bits in length [60]. IDEA works by encrypting and decrypting fixed-size blocks of data [59]. IDEA uses 64-bit blocks of data and 128-bit key size, and performs eight iterations for each block of data. The large key size makes IDEA very difficult to break because the time required to iterate through all possible key possibilities is too large. MD5 and SHA-1 are popular hashing algorithms, in which MD5 produces a hash value of 128 bits (16 bytes) [59] and SHA-1 produces a hash value of 160 bits [61]. In such research, the experiments show that the RC4 algorithm shows superior performance on 8-bit and 16-bit architectures compared to other schemes, especially in comparison to RC5. However, on 32-bit architectures, RC5 shows better compatibility with high-resource platforms than RC4. In addition, the computational cost of RC4, RC5, and IDEA is lower than that of hash algorithms (MD5 and SHA-1). In addition, the Advanced Encryption Standard (AES) is widely recognized for its advantages such as balancing low power consumption, high security, and good performance [62]. AES is chosen in many applications, especially in standard wireless technologies such as IEEE 802.15.4, which are commonly used in smart homes and industrial automation. In [63], the authors provide a comprehensive review of the latest lightweight AES architecture designs to explore the application possibilities of AES in WSN-IoT. The authors in [64] propose a low-power AES encryption architecture LPADA (Low-Power AES Data Encryption Architecture). The system was simulated using the Synopsys library with five different supply voltages. The experimental results show that 62.0% of dynamic power reduction and 88.5% of leakage power lowering were achieved compared to the power consumed by traditional AES data encryption. In addition, the key update procedure for LPADA shows effectiveness against replay and eavesdropping attacks by mutual authentication between end nodes and application servers.