# A Novel Encryption Scheme in Ship Remote Control against Differential Fault Attack
###### Abstract  
Cyber security has drawn more attention in the research of intelligent and unmanned ships. The remote control command transmitted in time sequence has a high similarity. This makes the ships more vulnerable to cyber-attacks, especially when they are controlled remotely. Aiming at the defense of Differential Fault Attack (DFA), this paper improved the SM4 algorithm in the phase of the S-box generation and circular encryption. The Wasserstein GAN Gradient Penalty (WGAN-GP) is used to generate S-boxes dynamically to confuse differential distribution tables. After the round encryption, the combination transformation is further applied to prevent from DFA. The corresponding symmetric decryption algorithm is also developed. Simulation result shows that the generated S-box meets the cryptography criteria and the combined transformation effectively hides the sensitive information in output ciphertext and guards against the DFA. intelligent ship; S-box; data security; encryption; remote control +
Footnote †: journal: Applied Sciences  
and complete direct control, indirect control, and situation processing [5]. Remote control instructions have the most significant impact on the safe navigation of ships. The data link layer of the ship CPS includes communication equipment such as a microwave and 5G. These devices are used to receive, and the remote control instructions sent continually by the shore-based control center to complete the expected navigation objectives, and feed back the ship's state and environmental parameters simultaneously, and then process these information. The amount of feedback data changes with the complexity of the system. The message data varies greatly in a short time, but the message data frame of the control instruction is short and has high reusability. Therefore, remote control instructions have higher requirements for data security. For this data, the security of using an asymmetric encryption algorithm is high. Still, the delay caused by large-scale asymmetric encryption and decryption has a potential impact on the stability of intelligent ship CPS [6]. Under complex sea conditions, there are risks such as ship remote control delay becoming larger and ships becoming out of control. Using a symmetric encryption algorithm can ensure data security with fewer system resources. However, the block cipher generally has poor protection against DFA, and the ship CPS has not designed facilities for encryption hardware protection. Thus, there are potential threats and vulnerabilities of DFA, which cannot meet the absolute security requirements of intelligent ship data transmission. [PERSON] and others applied blockchain technology to ensure the data security of industrial control systems meets the invariance and redundancy of data [7]. However, this technology has high requirements for computing power and the size of data space, and puts considerable pressure on the ship-end platform of CPS. With the continuous increase of historical data, the stability of the whole system cannot be guaranteed. [PERSON] et al. [8] designed a data security management system based on hybrid encryption, which uses a symmetric encryption algorithm to encrypt the original data, and an asymmetric encryption algorithm. Figure 1: CPS network structure of an intelligent ship. encryption algorithm to encrypt the symmetric key, which improves the security while ensuring the efficiency of data encryption. However, this method did not improve the poor protection of symmetric encryption algorithms against DFA. The development of neural network and complex network topology led to the realization that such an application is the next development direction of good cryptography. [PERSON] et al. [9] proposed a data encryption technology based on GAN, which takes the network itself as the encryption and decryption key. This method effectively migrates the attacks on the encryption algorithm itself, but fails to guarantee the performance in the case of a long key.