## 2 Point-to-Point QKD Mechanism  
This section describes the point-to-point QKD mechanism. BB84 protocol [13], the first QKD protocol, is the most technically mature protocol. In this protocol, the sender, [PERSON], encodes random binary bits using four single-photon polarization states, i.e., \"horizontal (\(|H{>}\))\", \"vertical (\(|V{>}\))\", \"\(+45^{\circ}\) (\(|+>\))\", and \"\(-45^{\circ}\) (\(|->\))\", and sends them to the receiver, [PERSON], via the quantum channel (QCh). \(|H{>}\) and \(|V{>}\) constitute the Z basis, while \(|+>\) and \(|->\) constitute the X basis, where the Z basis and the X basis are conjugate. Conventionally, suppose \(|H{>}\) and \(|+>\) represent the binary value 0, and \(|V{>}\) and \(|->\) represent the binary value 1. 0 and 1 are called qubits. The correct bit information is obtained when [PERSON] chooses the measurement basis corresponding to [PERSON] to measure the received single photon. When [PERSON] uses one measurement basis to measure the single-photon polarization state of another measurement basis, there is a 50% chance that he will receive different data from [PERSON]. The point-to-point QKD mechanism based on the BB84 protocol is introduced below, as shown in Figure 1. The QKD process consists of the following steps:  
1. [PERSON] generates two random sequences of the same length, \(\{a\}\) and \(\{a^{\prime}\}\), where \(\{a\}\) determines the chosen measurement basis and \(\{a^{\prime}\}\) determines the single-photon polarization state to be sent. [PERSON] prepares the single-photon polarization states (i.e., qubits, called raw keys) from the chosen random sequence and sends them to [PERSON] via QCh. 2. [PERSON] selects a random sequence \(\{b\}\) to determine the measurement basis, performs measurement for the received quantum states, and records the measurement results as \(\{b^{\prime}\}\). 3. [PERSON] announces the sequence \(\{a\}\) of the measurement basis chosen via the public channel (PCh). [PERSON] compares it with his own sequence \(\{b\}\) of the measurement basis. When they choose the same basis, [PERSON] and [PERSON] keep the data and convert them into bit information (called sifted keys); otherwise, the data is discarded. 4. [PERSON] and [PERSON] disclose part of the sifted keys to perform error estimation and calculate the corresponding quantum bit error rate. If the quantum bit error rate is higher than a set error threshold, the QKD process is terminated, and step 1 is repeated. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Schemes**} & \multirow{2}{*}{**Focus Points**} & **Security Probability/** & **Resource Utilization** & **Improvement Rate to** \\  & & **Success Rate** & & **Benchmark** \\ \hline \multirow{2}{*}{KoD [33]} & security requirements & \multirow{2}{*}{up to 1.0} & \multirow{2}{*}{-} & \multirow{2}{*}{-} \\  & of different services & & & \\ \hline \multirow{4}{*}{RWTA [34]} & static routing, & \multirow{2}{*}{up to 1.0} & wavelength utilization: & \multirow{2}{*}{time-slot utilization:} \\  & wavelength, & & up to 0.5; time-slot & \\  & and time-slot & & utilization: up to 0.75 & 0.16 \\  & assignment & & & \\ \hline \multirow{2}{*}{DSKP [35]} & the number of keys & \multirow{2}{*}{-} & time-slot utilization: up to 0.55 & \multirow{2}{*}{-} \\  & in QKP & & & \\ \hline \multirow{2}{*}{DDKA [36]} & requirements of the IoT & \multirow{2}{*}{up to 0.95} & \multirow{2}{*}{-} & SR: up to 0.26 \\  & application & & & \\ \hline \multirow{4}{*}{ADA [37]} & key volume, key & \multirow{4}{*}{up to 1.0} & \multirow{2}{*}{-} & SR: 0.11 on average \\  & update rate and path & & & \\ \cline{1-1}  & hops required by the & & & \\ \cline{1-1}  & application & & & \\ \hline \multirow{2}{*}{RAWC (our scheme)} & resource status of the & \multirow{2}{*}{up to 1.0} & wavelength utilization: & \multirow{2}{*}{SR: up to 0.3} \\  & network and & & up to 0.9 & \\ \cline{1-1}  & wavelength conflicts & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The comparison of the related schemes with the RAWC scheme.