# Comparison of Distributed Tamper-Proof Storage Methods for Public Key Infrastructures
## 5 Performance Comparison
### Authentic Message Sending-Phase 2  
The second phase of the NFC-KE is, in terms of real-world impact, the most important since the corresponding execution times will directly influence the responsiveness of the system. Generally, Phase 2 is querying the file storage system for the given Sensor Node's public key to verify the message signature, originating from said Sensor Node. Therefore, lower execution times will allow for faster message processing. A significant differentiation needs to be made between the two phases because Phase 1 must be executed only once for each Sensor Node, whereas Phase 2 is executed repeatedly afterward. Thus, the impact of particularly bad Phase 1 execution times is less significant than comparatively high execution times in Phase 2.  
For the performance comparison in Phase 2, the number of simultaneously sending Sensor Nodes influences the general performance of the Signing Hub. Therefore, the following evaluation will, additionally, include performance numbers for one to six simultaneously sending Sensor Nodes that are virtualized and sending data within an interval of one to two seconds. The following Figure 5 shows the mean execution times of each DLT scenario and also differentiates between each Sensor Node configuration.  
As can be seen, by the resulting mean execution times, the number of Sensor Nodes does, in this case, not influence the performance numbers in a significant way. In the case of the IPFS-based solutions, these are almost neglectable. Again, the private IPFS deployments offer the lowest execution times at almost 60 ms constantly. The Filebase setup is considerably faster than the HLF approach with a 150 ms mean execution time. The general pattern that already set itself apart in Section 5.1 does repeat itself in this case, since the Sia Skynet solutions also take the most time for Phase 2 execution with over 310 ms mean execution time. Note that for this comparison leaving out the SkyDB functionality like previously described in Phase 1 (cf. Section 5.1) does not apply here, since the message-sending part is inherently reliant on the public key query functionality. When comparing the IPFS-based solutions, only the Web3.Storage approach falls behind the Phase 2 execution times of the HLF-based approach.  
To get a deeper understanding of the Sensor Node number's influences, Figure 6 shows the particular execution times of the IPFS private scenario using eight peers within the network.  
Figure 5: NFC-KE Phase 2 mean execution time comparison.  
Here, the mean and median execution times remain almost constant among all tested Sensor Node numbers. The standard deviation and the number of outliers increase proportionally with increasing numbers of Sensor Nodes. Thus, the reliability of the system is slightly decreasing. This effect is only noticeable when visualizing the performance numbers for the private IPFS setup. Other DLT setups do not show the given behavior, due to other effects being more influential to the generally longer execution times such as latency, network bandwidth, and congestion.