## 4 End to End Security Analysis on the Proposed IIoT Security Architecture
### Transport Layer
#### 4.2.1 Capillary Network and Communication Technologies  
The capillary network is defined as a local network that is intelligently connecting \"things\" (e.g., sensors, actuators, embedded devices) via short-range radio access, power link communication or infrared technologies [79; 80]. These communication technologies include IrDA, Bluetooth, radio frequency identification (RFID), near field communication (NFC), INSTON, Bluetooth, Bluetooth low energy (BLE), EnOcean, ultra-wideband (UWB), ANT+, HomePlug, ZigBee, WirelessHART, ISA110.11a and Thread [79; 80; 81; 82; 83; 84], as illustrated in Figure 2. The detailed security analysis of these technologies is further summarised in Table 7.  
Generally, most capillary communication technologies are radio waves-based and wireless, except for IrDA and HomePlug, which use infrared light and power link communication. These wireless and radio waves-based communication technologies are generally vulnerable to wireless network threats, man-in-the-middle attacks, unauthorized message resource misappropriation. Meanwhile, the Bluetooth, BLE, WirelessHART and Thread technologies, exposure a higher security risk operating on popular radio frequency--2.4 GHz ISM band. Although most of them follow the IEEE 802.11 security standard, however, still subjected to a broad-spectrum jamming attack, 802.11 frame injection, 802.11 data replay, 802.11 Beacon, and authenticate flooding attack. Compared to others, UWB enjoys more robust security features as it operates on very low radiated power and narrow pulses, which increases wireless attack difficulties.  
At the edge of IIoT networks, the ongoing security challenges such as interoperability issues of different security mechanisms (e.g., incompatibility of AES encryption in multi-channel mode), scalability of key management and distribution, stronger and lightweight cryptography algorithm in the constrained resource of \"things (low power, energy, storage size) and end-to-end communication and data protection across the heterogeneous interface are urgently called for a realization of a complete IIoT vision.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Technology /Standard**} & \multirow{2}{*}{**Features/ Functionalities**} & \multicolumn{5}{c}{**Analysis of Security**} & \multirow{2}{*}{**Deployed Security Countermeasures**} & \multirow{2}{*}{**Ongoing Challenges and Future Works**} \\ \cline{3-4} \cline{6-9}  & & & & & & & & & \\ \cline{3-4} \cline{6-9}  & & & & & & & & & \\ \hline \multirow{5}{*}{IrDA} & \multirow{5}{*}{Use infrared light in a range of \(<\)1 m; Application: remote control, data transfer} & \multirow{5}{*}{\(\times\)} & \multirow{5}{*}{\(\times\)} & \multirow{5}{*}{\(\times\)} & \multirow{5}{*}{\(\times\)} & \multirow{5}{*}{\(\times\)} & \multirow{5}{*}{\(\times\)} \\  & & & & & & & & & \\ \cline{1-1} \cline{4-7}  & & & & & & & & & \\ \cline{1-1} \cline{4-7}  & & & & & & & & & & \\ \cline{1-1} \cline{4-7}  & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 7: Security analysis on capillary network communication technologies.