# Wireless and Fiber-Based Post-Quantum-Cryptography-Secured IPsec Tunnel
## 2 Related Works  
Since the NIST started the competition for the standardization of PQC algorithms, a lot of work on the implementation of the presented PQC algorithms has been performed. Those efforts have not only been focused on Central Processing Unit (CPU) implementations but also on a variety of platforms such as FPGA [21; 22], GPU [23], RISC-V [24; 25], or a combination of different platforms [26] to improve the performance of the computationally challenging parts of the PQC algorithms. The Number Theoretic Transform (NTT) method, for example, is a mathematical operation of fundamental importance for Falcon [14], Dilithium [15], and Kyber [16]. NTT serves for the efficient multiplication of polynomials. The procedure can be parallelized, and hence, the performance benefits strongly from implementations on platforms that can provide heavy parallelization such as FPGAs [27] or GPUs [28]. Other subroutines or functions of PQC algorithms are recursive and therefore do not benefit from parallelization. As an example, Falcon uses floating point operations and recursive functions which would require a modification prior to being implemented in hardware. In [29], the authors state that their implementation of Falcon's key generation on a FPGA shows a high latency while having high hardware utilization compared to a software-based implementation on an Intel I7 CPU. The IPSec protocol has existed for decades. Therefore, numerous publications with different implementations on a large variety of platforms have been reported. In [30], the authors compare IPSec solutions implemented in Data Plane Development Kit (DPDK), in the Linux userspace, in the Linux kernel, on the Network Interface Card (NIC), and on the host CPU. They claim a 3.54\(\times\) improvement in throughput and a 2.54\(\times\) improvement in latency with their implementation compared to the existing control plane design. They achieve a 4.795 Gbit/s throughput. However, they achieve this throughput using 128-bit AES Galois-counter mode (GCM). For being considered quantum-safe, AES-256 must be used [7]. In [31], the authors examine the reference implementations of Dilithium and Kyber on data processing unit (DPU) devices and how the algorithms can be accelerated using an optimized version for ARM core processors. In [32], the authors use a PQC software stack similar to the one that we present in this work. They investigate the performance impact of Falcon and Kyber in the stack and evaluate the advantages and disadvantages of choosing one over the other. In [33], an IPsec tunnel using Dilithium and Kyber with a different software stack and a different methodology is established. In the work that we present here, we apply our knowledge about PQC and focus on establishing a PQC-secured IPsec tunnel. In the context of quantum-secure communication, it is necessary to mention Quantum Key Distribution (QKD). While PQC is based on mathematical challenges, the security of QKD relies on the physical properties of quantum mechanics to achieve secure communications. In [34], the authors report on a 10 Gbit/s IPsec tunnel between two JP Morgan Chase data centers. QKD is a highly important approach to securing future networks against attackers. However, unlike PQC, QKD requires extensive specialized hardware. Moreover, the rate at which quantum-safe keys are exchanged is low. Consequently, a key management system [35] is required, which increases the overhead and complexity of such systems. Given the high costs associated with QKD, we expect it to be used primarily in areas with very high security needs, such as military or government applications. We envision a co-existence of PQC and QKD systems in the form of hybrid PQC-QKD schemes [35]. Despite extensive research on PQC and IPsec individually, little has been reported on the integration of PQC with IPsec. In [36], the authors use PQC in a custom protocol and combine it with IPsec. However, they neither use Falcon [14] nor report on the throughput achieved with their IPsec implementation.