# Signature Split Method for a PQC-DSA Compliant with V2V Communication Standards
## 4 Experiments  
We used an NVIDIA Jetson AGX Xavier as our target OBU which contains a 64-bit ARM A5x processor with 32 GB of RAM, 32 GB of storage, and a 512-Core Volta GPU with 64 Tensor Cores (8 SM, 64 kB register, 128 kB shared memory). All PQC-DSA code for our simulation wa compiled with gcc with -shared, -O3 options and integrated into V2 Verifier in the form of a dynamic library. The benchmark used exactly the method described in the simulation process and performed two tests. The first was when the remote and local cars made up the first session, and the second simulation was when the remote and local cars communicated in successive sessions. Each API was calculated with 300 average values. Dummy operations were inserted in between to avoid using cache memory, and this process was excluded when performance was measured. The \"_run_remote_\" APIs were configured in multiprocessing. The operating environment was the 4.4.0-59-generic kernel version Linux. In the advanced mode of the C-V2X protocol, we did not consider our method of splitting and merging packets because splitting does not occur during the transmission of packets. For the simulation of the WAVE protocol, we experimented with \"_Simple split way_\" and \"_Split way for Crystals-Dilithium_\", respectively. However, as a result of the actual experiment, the execution time of the two methodologies was almost the same, so we mainly report the results of \"_Split way for Crystals-Dilithium_\".  
Tables 3 and 4 show the measurements including [generating payload + generating key pair + generating Signature + verifying signature] for an average of 300 payloads on the WAVE and C-V2X protocols, respectively. In this scenario, when the remote and local cars first configure a session, \"_run_remote_\" API runs the key generation process of PQC-DSA. Unfortunately, there is no open-source code for [7], as far as we know. Therefore, we reconstructed the simulation proposed in [7].  
Table 3 is a simulation assuming communication in the advanced mode of the C-V2X protocol. In C-V2X, the maximum BSM packet size is 12,000 bytes, making it easy to load the signatures of each PQC-DSA. Therefore, correctness can be satisfied in any case. Since we use an optimized PQC-DSA implementation, there is a performance improvement compared to the reference-based simulation.  
Table 4 is a simulation assuming communication with the WAVE protocol. The signature of Crystals-Dilithium is split and transmitted due to the limitation of packet size. The splitting and combining packets processes occur in \"_run_remote_\" and \"_run_local_\" API, respectively. Therefore, even though we ran the same signature generation and verification process, a small amount of latency compared to the results of C-V2X simulation occurred. As in previous research, the reference-based results of Crystals-Dilithium did not achieve  
Figure 3: Simulation of the WAVE protocol using “_Split way for Crystals-Dilithium_” for 10 remote cars.  
correctness in the WAVE protocol. However, in our simulation results with the \"_Split way for Crystals-Dilithium_\", correctness was satisfied.  
Table 5 shows the measurement result of maximum termination delay time in \"_run_remote_\" and \"_run_local_\" marked by (\(\frac{\textit{run\_remote}}{\textit{run\_local}}\)). This scenario assumes continuous communication between the remote car and the local car. The remote car already has the private key, and the local car knows the public key of the remote car. Similar to the result ub Table 4, our simulation achieves correctness for all PQC-DSAs. In addition, there is a performance improvement compared to the previous work due to the application of an optimized PQC-DSA.