Tokyo – April 9, 2026 – TOPPAN Holdings Inc. (TYO: 7911) (TOPPAN Holdings), the National Institute of Information and Communications Technology (NICT), and ISARA Corporation (ISARA) have successfully conducted a proof of concept confirming the effectiveness of technology for seamless migration from current cryptography to Post-Quantum Cryptography (PQC) for certificate authority frameworks that form the base of the security infrastructure of internet communications. The security of internet-based communications is supported by digital certificates that verify the identities of communicating entities and public-key infrastructure1 based on certificate authorities that issue and sign certificates. However, there is a risk that current public-key cryptosystems could be vulnerable to attacks from quantum computers in the future, necessitating a prompt migration to PQC. At the same time, the transition phase could see service disruptions or outages when new cryptographic algorithms are applied to root certificate authorities, which serve as the foundational trust anchors for security infrastructure. ISARA has developed digital certificates issued via a secondary crypto-agile root certificate2 to facilitate migration from current cryptography such as ECDSA3 to PQC algorithms such as ML-DSA.4 In the proof of concept, this secondary root certificate was integrated into a smart card system developed by TOPPAN Holdings on a quantum cryptography network testbed constructed by NICT. The ability to transition smoothly to PQC without disruption to existing authentication infrastructure was demonstrated through simulation of a transitional phase ecosystem in which both current cryptography and PQC are used for smart-card-enabled ID verification and internet access. This will help enable a phased migration to security levels sufficient to counteract the threat of quantum computers without interrupting services in sectors such as healthcare, finance, and government, where confidentiality must be maintained for extended periods. A part of the work was performed for Council for Science, Technology and Innovation (CSTI) Cross-ministerial Strategic Innovation