## 2 Preliminary Knowledge
### Advanced Encryption Standard (AES) Encryption Algorithm  
AES is a symmetric encryption algorithm that is widely used to secure sensitive data. Its main features include high security, efficiency and flexibility. The core idea of an AES encryption algorithm is to obfuscate the plaintext through multiple rounds of substitution and replacement operations using a key to finally generate the encrypted ciphertext. Because of its high security and efficiency, AES has become the encryption  
Figure 2: TLS protocol architecture diagram. algorithm of choice for many security applications, such as network communication, data storage and encrypted files. In this paper, an AES encryption algorithm was selected as the basis for optimization, and DES and other encryption algorithms were not selected; the main reason is that AES has higher security and wide application prospects. Compared with DES, AES uses a larger key length (128, 192 or 256 bits), which can effectively resist brute-force attacks. In addition, the block encryption structure of AES adopts more flexible operations such as subbyte substitution, row shift and column obfuscation, which has higher diffusion and confusion and significantly improves the ability to resist differential attack and linear attack. Although DES has the advantages of a simple structure and low hardware implementation cost, it is no longer suitable for scenarios with high security requirements under modern computing capabilities because it only supports 56-bit keys. Therefore, this paper chose an optimization scheme based on AES, and further improved its encryption efficiency by combining it with a preprocessing mechanism to meet the efficient security requirements of large-scale data transmission. Many researchers are now applying AES encryption algorithms to specific practical applications. [PERSON] used Advanced Encryption Standard (AES) as a secure and flexible encryption scheme, which can improve AES performance by 42% compared to traditional CPU implementations by reducing the data movement and increasing the memory bandwidth [16]. [PERSON] proposed a Smart Recovery Authorization Model (SRAM-AES) to address the security challenges in chaotic systems by applying AES encryption to deal with authorization issues, ensuring stable controller operation and avoiding production failures [17]. [PERSON] proposed an application-layer security framework that implements a low-cost hardware-software scheme with real-time lightweight application-layer AES encryption to ensure that, even under unfavorable transmission conditions, it is possible to achieve continuous data encryption for secure data transmission [18]. [PERSON] and [PERSON] proposed a modified scheme for AES-related problems that included reducing the number of rounds, replacing S-boxes to reduce the requirements and applying AES to specific encryption modes to solve the mode appearance problem [19]. [PERSON] proposed a scheme based on logistic chaos mapping and Advanced Encryption Standard (AES) for image encryption. The survey and experimental results showed that the proposed algorithm outperformed many image encryption algorithms in terms of statistical and differential attacks [20]. [PERSON] proposed an S-box generation algorithm based on a 4D hyper chaotic system and improved particle swarm optimization. An image encryption algorithm was designed by using generated S-boxes and it improved the security of S-boxes. The experimental results showed that the designed S-box had good performance in five metrics: nonlinearity, SAC, BIC-NL, LP and DP [21]. [PERSON] proposed an encryption technique to protect the proposed system against passive and active attacks. The proposed technique is a hybrid of RivestShamirAdleman and Advanced Encryption Standard 256 (AES256+RSA). The authors used this hybrid approach to efficiently and secretly share users' keys, and the simulation results showed that the system provides security, scalability, optimized data storage, trustability of nodes, and transparent data sharing [22].