Public Key Infrastructure (PKI) generates and distributes digital certificates to provide the root of trust for securing digital networking systems. To continue securing digital networking in the quantum era, PKI should transition to use quantum-resistant cryptographic algorithms. The cryptography community is developing quantum-resistant primitives/algorithms, studying, and analyzing them for cryptanalysis and improvements. National Institute of Standards and Technology (NIST) selected finalist algorithms for the post-quantum digital signature cipher standardization, which are Dilithium, Falcon, and Rainbow. We study and analyze the feasibility and the processing performance of these algorithms in memory/size and time/speed when used for PKI, including the key generation from the PKI end entities (e.g., a HTTPS/TLS server), the signing, and the certificate generation by the certificate authority within the PKI. The transition to post-quantum from the classical ciphers incur changes in the parameters in the PKI, for example, Rainbow I significantly increases the certificate size by 163 times when compared with RSA 3072. Nevertheless, we learn that the current X.509 supports the NIST post-quantum digital signature ciphers and that the ciphers can be modularly adapted for PKI. According to our empirical implementations-based study, the post-quantum ciphers can increase the certificate verification time cost compared to the current classical cipher and therefore the verification overheads require careful considerations when using the post-quantum-cipher-based certificates.

Quantum computing challenges the mathematical problems anchoring the security of the classical public key algorithms. For quantum-resistant public key algorithms, the National Institute of Standards and Technology (NIST) has undergone a multi-year standardization process and selected the post-quantum cryptography (PQC) public key digital signatures of Dilithium, Falcon, and SPHINCS⁺. Finding common ground to compare these algorithms can be difficult because of their design differences, including the fundamental math problems (lattice-based vs. hash-based). We use a visualization model to show the key/signature size vs. security trade-offs for all PQC algorithms. Our performance analyses compare the algorithms’ computational loads in the execution time. Building on the individual algorithms’ analyses, we analyze the communication costs and implementation overheads when integrated with Public Key Infrastructure (PKI) and with Transport Layer Security (TLS) and Transmission Control Protocol (TCP)/Internet Protocol (IP). Our results show that the lattice-based algorithms of Dilithium and Falcon induce lower computational overheads than the hash-based algorithms of SPHINCS⁺. In addition, the lattice-based PQC can outperform the classical algorithm with comparable security strength; for example, Dilithium 2 and Falcon 512 outperform RSA 4096 in the TLS handshake time duration.

Domain Name System Security Extensions (DNSSEC) uses public-key digital signatures to provide integrity and authentication for DNS query responses. The current standardized DNS for reliable UDP delivery limits DNS response (including the message, signature, and public key) to a maximum of 1232 bytes. Incorporating NIST's post-quantum digital signatures into the DNS protocol results in a response size that exceeds the limit set by the Ethernet standardization, making PQC incompatible with the current standardized DNS. To address the incompatibility and enable PQC to protect the authenticity against the quantum-equipped adversaries, previous research proposed fragmenting the DNSSEC messages. Fragmentation however exposes DNSSEC to Fragmentation Mis-Association threat, traditionally studied in the broader IP fragmentation contexts and not applicable in the current DNSSEC with classical/pre-quantum cipher (no fragmentation needed). We distinguish our work from the previous research incorporating PQC to DNSSEC to defend against the Fragmentation Mis-Association Threat by chaining the fragments and applying cryptographic commit-and-reveal. We also advance the previous research and further reduce the number of packet fragments, which can be particularly useful as the DNSSEC based on UDP is prone to packet transmission failure increasing the chance of the DNS response failure when sent in multiple fragments, by using blockchain to offload and enable the offline delivery of the public key. Our scheme thus even allows the Falcon-512 PQC cipher incorporation to forgo the fragmentation, in contrast to the previous research requiring fragmentation for Falcon-512; the other PQC ciphers, i.e., Dilithium ciphers and Falcon-1024, still require fragmentation in our scheme due to the standardized signature sizes. We implement our scheme and analyze the effectiveness and performances through experimentation.

coronary artery disease (CAD) remains a prevalent cardiovascular condition, posing significant health risks worldwide. Accurate segmentation of coronary arteries from coronary computed tomography angiography (CCTA) images is crucial for diagnosis and treatment planning. Despite advancements, coronary artery segmentation (CAS) remains a significant challenge due to the considerable variability in the scale of coronary arteries, the complex anatomical structure and morphology, and the low contrast between blood vessels and the surrounding tissue. To effectively tackle these issues, we propose an attention-guided feature-aggregated network (AGFA-Net) specifically designed for CAS using CCTA images. AGFA-Net leverages attention mechanisms, feature refinement and hierarchical feature aggregation to capture salient features, acquire a more distinctive semantic representation and enhance segmentation accuracy. Evaluation on a dataset comprising 1,000 CCTAs demonstrates AGFA-Net's superior performance, achieving an average Dice coefficient similarity of 86.74 % and a 95% Hausdorff distance of 0.82 mm during 5-fold cross-validation. Ablation studies further validate the effectiveness of the proposed modules, highlighting their contributions to improved segmentation accuracy. Overall, AGFA-Net offers a robust and reliable solution for CAS, addressing challenges posed by varying arterial sizes, complex anatomies, and low image contrast.