# Cyber-Security Threats and Side-Channel Attacks for Digital Agriculture
## 4 Side-Channel Attacks  
A communication system consists of devices and communication channels. Reasonable security is obtained by accessing devices only with secret credentials and encrypting the communication channel. Side-channel attacks are related to extracting information from the data leakage during the communication or while accessing the system. A related concept to the side-channel is the covert channel used to communicate stealthily either to avoid listeners in the middle or exfiltrate information. Side-channel and covert attacks leverage the physical properties of the hardware, software, or transmission medium to extract useful sensitive information from the internal functioning and operation of the targeted device [35]. In 1996, [PERSON] [36] demonstrated that timing data in the cryptographic implementation could be used to recover the entire secret key. With the proliferation of smart devices, IoT, sensors, and slack cryptographic implementation on the hardware, various side-channel attacks have been discovered to break the encryption and extract sensitive credentials. Side-channel attacks are categorised into physical and functional [37]. The physical categorisation is based on a measurable quantity that is the by-product of the implementation. Examples are power output, electromagnetic emission, clock timing, user interaction, acoustic, optical, thermal, and network inference (wired/wireless). The functional type is based on the internal functional implementation and computing system working that could leak the data. Examples are memory implementation, CPU/GPU architecture, and software/firmware cryptographic implementation/coding. Figure 2 provides a snapshot of various side-channel attacks for a DigAg application. All the physical and functional SCAs are possible on any DigAg applications since most applications are deployed in a harsh environment, not monitored, operated by a non-technical person, and sparsely used. Secret key leakage would lead to all other attacks as mentioned in Section 3. Table 2 shows the SCAs as reported in the literature. The previously reported SCAs are mostly for computer systems. SCA analysis for IoT devices [15] is closely related to DigAg. The DigAg systems consist of small sensors attached to highly computational devices (drones, autonomous robots). Unlike computer systems, they are unattended and deployed in a harsh environment. Further, their use is infrequent and monitored by a non-technical person. Therefore, the malicious user has limited freedom to play with and change different parameters to reveal sensitive information. A malicious user can install a hardware Trojan to capture and transmit information in the worst-case scenario. For example, power usage SCAs can be easily carried out with physical access to devices. (e.g., smart homes), the physical access would be relatively difficult compared to digital agriculture, where agriculture equipment is deployed and left in the field. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**SCA Threats** & **Method and Techniques** & **Explanation** & **Implication to DigAg** \\ \hline Microarchitectural (MA) [35] & Speculative execution, branch prediction, data flow analysis, reverse engineering & Malicious user & Most of the equipment is vulnerability in hardware and software & Model of the equipment is deployed \\  & engineering & optimisation & engineering and \\  & & features of the computer system & \\  & & (CPU, GPU) to & compromise \\  & & reveal secret & secret keys. \\  & & information. & \\ \hline Power usage [14] & Simple power analysis, correlation power analysis, execute different analysis, USB power analysis, consumption to execute different instructions. The analysis, USB analysis of energy consumption to execute different instructions can be used to extract secret information. & Like MA, voltage and current analysis could be easily carried out with physical access to the devices. \\  & & & \\ \hline \hline \end{tabular}
\end{table}