# A Practical Implementation of Post-Quantum Cryptography for Secure Wireless Communication +
## 6 Evaluation
### Results and Discussion
#### 6.2.5 Impact of the PQC Algorithm on Performance in the Video-Streaming Use Case  
To demonstrate the impact of PQC algorithms on real-time applications such as video streaming, we evaluated the proposed protocols using a video-streaming application, as described in Section 4.1.1. We measured the overall throughput and retransmission rate as metrics. However, PQC algorithms are not suitable for applications such as video and live streaming in their current form without substantial optimization due to the large ciphertext size, which results in continuous freezes of video frames caused by the frequent retransmission of frames. Therefore, to evaluate the performance of our proposed protocol, we utilized the hybrid protocol and compared its performance with that of conventional AES-256. In our evaluation, we streamed a short pre-recorded \"MP4\" video with the following properties: a total size of 17 MiB, a resolution of 1920 \(\times\) 1080, 30 frames per second, a bitrate of 2.863 Mbps, and a duration of 47 s 249 ms. The server acquired each frame from the video file and encoded it before encrypting it. The encrypted frames were transmitted sequentially as rapidly as possible without limiting the rate. On the other hand, the client (stream viewer) decrypted and decoded each received encrypted frame. These frames were rendered using an OpenCV window for viewing the stream. The display loop included a standard 1 ms delay (i.e., cv2.waitkey(1)), which is necessary for OpenCV to process GUI events and refresh the displayed frame. This delay also allows for user interaction  
Figure 10: Chat average round-trip times: (**a**) PQC–AES-256 (with F512). (**b**) PQC–AES-256 (with F1024). (**c**) PQC standalone (with F512). (**d**) PQC standalone (with F1024). (e.g., capturing user input, such as 'q' for quitting the stream). The delay is an attribute of the OpenCV GUI mechanism used for the experiment and is not part of the processing overhead of the proposed protocols. Throughput  
We measured the total throughput, which reflects how many encrypted video frames can be successfully transmitted. Since the user experience in video streaming is important, we measured the metrics from the client side. Figure 11 shows the total throughput achieved for streaming an encrypted video over the network. An almost constant total throughput was observed across all PQC algorithms. The results shown in Figure 11a show an approximate total throughput of 22 Mbps for K512-F512 and K768-F512 compared to the other algorithms and conventional AES-256. The other algorithms used in the hybrid protocol achieved a slightly lower approximate total throughput (20.1 Mbps) than conventional AES-256 (20.8 Mbps). Furthermore, as shown in Figure 11b, a similar trend was observed for the KEM algorithms paired with F1024, with almost all the algorithms achieving a slightly lower total throughput compared to the performance of AES-256, except for K1024-F1024, which achieved the highest total throughput of 21.6 Mbps, an 0.8 Mbps increase compared to conventional AES-256. The pairs BIKE-L3-F1024, BIKE-L5-F1024, HQC-128-F1024, and K768-F1024 achieved the lowest total throughput of approximately (19 Mbps) compared to all the other algorithms. Additionally, we measured the TCP retransmission rate. A higher retransmission rate indicates an increase in packet loss, often due to network congestion, which can result in freezes or buffering in the video stream. The results shown in Figure 12a confirm lower retransmission rates ranging from 0.05% to 0.20% for most algorithms in the hybrid protocol, except for BIKE-L1-F512, HQC-192-F512, K768-F512, and K1024-F512, which showed retransmission rates above 0.20%. BIKE-L5-F512 achieved the lowest retransmission rate, with 0.05% of the total encrypted frames streamed. Similarly, the pairs BIKE-L3-F512 (0.16%), HQC-128-F512 (0.16%), HQC-256-F512 (0.20%), and K512-F512 (0.15%) achieved lower retransmission rates than AES-256.