# A Practical Implementation of Post-Quantum Cryptography for Secure Wireless Communication +
## 6 Evaluation
### Results and Discussion
#### 6.2.4 Impact of PQC Algorithms on Performance in the Chat-Based Use Case  
It was observed that the proposed protocols with various PQC algorithms are more suitable for the chat-based use case in comparison to the AES-256 conventional method. Figure 9 shows the performance of the protocols in maintaining end-to-end encryption similar to those in modern chat applications. Figure 9a shows the results when PQC KEM algorithms were paired with the F512 signature algorithm in hybrid mode. A lower processing time between 61 s and 73 s was achieved by all algorithm pairs than the conventional AES-256 algorithm, which recorded a total processing time of 80 s. For the BIKE algorithms, BIKE-L5-F512 achieved the lowest time of approximately 61 s, while for the HQC algorithms, HQC-256-F512 achieved the lowest time (63 s), and for the CRYSTALS-Kyber algorithms, K1024-F512 achieved the lowest time (64 s). As shown in Figure 9b, when the signature algorithm F1024 was paired with each KEM algorithm, the total processing time ranged from 64 s to 69 s, with most of the algorithms achieving processing times similar to when the KEM algorithm was paired with F512. BIKE-L3-F1024 (64 s) and K1024-F1024 (64 s) achieved the lowest processing times compared to the other algorithms. However, slightly higher processing times were observed for the PQC standalone protocol. According to the results in Figure 9c, the CRYSTALS-Kyber algorithms achieved higher processing times for K512-F512 (77 s), K768-F512 (96 s), and K768-F512 (74 s). A similar trend was observed when F1024 was used, as shown in Figure 9d, with a lower processing time for K768-F1024 (73 s), while the time increased for K512-F1024 (85 s). The HQC algorithms maintained almost consistent processing times compared to the hybrid protocol, with slight variations of less than 5 s. Conversely, BIKE experienced higher processing times in the PQC standalone protocol than in the hybrid protocol but lower processing times than the conventional AES-256 algorithm, as shown in Figure 9a,c. With the exception of K768-F512 and K512-F1024, which achieved higher processing times \begin{table}
\begin{tabular}{c c c c} \hline \hline
**User 1** & & **User 2** & \\
**Text Message** & **Size (Bytes)** & **Text Message** & **Size (Bytes)** \\ \hline Hello & 5 & Hi, how are you? & 16 \\ I’m good, thanks. And you? & 26 & You are welcome. I’m fine too. & 30 \\ Are you ready for the demo? & 27 & Yes, all set. Let’s get started! & 32 \\ Great! Here’s the first part of the code. & 60 & Looks interesting. I have a few questions & 60 \\ What do you think? & & about the results. & \\ Sure, I can explain anything about it. & 38 & Thanks! I want to know how you handled & 67 \\  & & the data preprocessing step. & \\ I used the standard normalization method & 57 & That makes sense. Let’s move on to the & 52 \\  & and added custom & next section. & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Examples of text messages. than AES-256 in the PQC standalone protocol, all algorithms in this mode experienced lower overheads and are expected to function effectively without adversely impacting the QoS of a chat-based application. Round-Trip Time  
The end-to-end delay likely to be introduced by the proposed protocols was measured using the average RTT. It was expected that a delay for small, bursty messages, including delays due to encryption, network transit, and decryption, might occur. Therefore, the RTT, which is important in interactive chat, was considered. Figure 10 shows the average RTTs of the end-to-end delay of the proposed protocols. It was observed that the proposed protocols achieved better performance than conventional AES-256, which had an average RTT of 2.44 ms. According to the results shown in Figure 10a,b for the hybrid protocol, an average RTT of less than 1.5 ms was observed for all algorithms, except for K512-F512 (1.66 ms), K768-F512 (1.51 ms), and K512-F1024 (1.52 ms).