# An On-Demand Fault-Tolerant Routing Strategy for Secure Key Distribution Network
## 5 Simulations and Discussion
### Results and Discussion
MPCS has the lowest KMU due to the resource consumption caused by its mechanism. When the other two methods correctly implement routing control, it will not increase the local key overhead in other places due to the improvement of FNR. The proposed solution provides significant PDR gains as mentioned above. This is due to the improved fault tolerance of the system at the cost of resource consumption. In general, the KMU difference between these three methods is small, reflecting the effective resource utilization of the proposed solution. For example, when the number of nodes is 100, with the improvement of PDR, the KMU of the proposed solution is even better than the comparison method at FNR around 0.2 to 0.3. **Corrupted Key Ratio**: Figure 11 shows the corrupted key ratio (CKR) of the three methods under FNR in the BHA scenario of 60 nods. The CKR of different methods increases with the increase of FNR, and the rate of increase of the proposed solution is much lower than that of the comparison method. This is one of the advantages of the proposed solution, although MPCS has lower CKR than OSPF and ASR when FNR is low. However, as FNR increases, there are not enough redundant paths in the network for key distribution, which leads to a sharp increase in CKR under MPCS. Through the collaborative work of the proposed solution, the proposed solution is more accurate than the proposed solution. Figure 8: PDR comparison of the proposed solutions in the BHA scenario, i.e., OSPF, ASR, and MPCS. (a) Number of nodes = 40. (b) Number of nodes = 60. (c) Number of nodes = 80. (d) Number of nodes = 100.  
fault detection mechanism and the path discovery mechanism, a suitable path is found for communication key distribution by the proposed strategy, which reduces the possibility of the communication key being intercepted by faulty nodes. When the maximum FNR is equal to 0.4, the CKR is still less than 5%. This information leakage can be eliminated with privacy amplification. Since the path provided by OSPF and ASR is relatively fixed, CKR is linearly positively correlated with FNR, which greatly improves the possibility of communication key leakage. **Hop Count**: Figure 12 shows the hop count of the three methods under FNR in the BHA scenario of 60 nods. OSPF identifies a single shortest path for key distribution. ASR and MPCS selects other subshort paths for key distribution with a certain probability, thereby improving the distribution success rate and therefore having a larger hop count. As FNR increases, a slight decrease in hop count can be observed. This is essentially due to the lack of response measures to faulty nodes in the comparison method, which results in a greater possibility of containing faulty nods in long paths, resulting in a decrease in the distribution success rate. The hop count traversed by successfully received communication keys is reduced. In the absence of faulty nodes, benefiting from the reasonable definition of link status, the hop count of the proposed solution is between OSPF and ASR, which also represents a lower distribution delay. The increase of hop count with the increase of FNR means that the proposed solution can identify faulty nodes and find paths that cannot be found by the comparison method for key distribution, which improves the fault tolerance of the strategy. Figure 9: PDR comparison of the proposed solutions in the TRA scenario, i.e., OSPF, ASR, and MPCS. (**a**) Number of nodes = 40. (**b**) Number of nodes = 60. (**c**) Number of nodes = 80. (**d**) Number of nodes = 100. Figure 11: CKR comparison of the proposed solutions in the BHA scenario. Figure 10: KMU comparison of the proposed solutions in the BHA scenario, i.e., OSPF, ASR, and MPCS. (**a**) Number of nodes = 40. (**b**) Number of nodes = 60. (**c**) Number of nodes = 80. (**d**) Number of nodes = 100.