Post-Quantum Cryptography Guide: How Businesses Should Prepare for the Quantum Threat in 2026

The Quantum Computing Threat to Current Encryption

The rapid advancement of quantum computing poses a fundamental threat to the encryption technologies in widespread use today. RSA and Elliptic Curve Cryptography (ECC) derive their security from the computational difficulty of integer factorization and discrete logarithm problems, respectively. However, running Shor's algorithm on a quantum computer would solve these problems efficiently, rendering these cryptographic systems vulnerable. As of 2026, a Cryptographically Relevant Quantum Computer (CRQC) capable of breaking these algorithms has not yet been realized, but most experts project this milestone will be reached in the 2030s. IT companies across Tokyo's Shinagawa and Minato wards have begun actively discussing preparations for this "quantum threat." If current encryption is compromised, every domain of social infrastructure — online banking, electronic commerce, digital government — would be affected, making early preparation critically important.

NIST-Standardized Post-Quantum Cryptography Algorithms

The National Institute of Standards and Technology (NIST) officially published its post-quantum cryptography (PQC) standard algorithms in 2024. ML-KEM (formerly CRYSTALS-Kyber) was selected as the standard key encapsulation mechanism, while ML-DSA (formerly CRYSTALS-Dilithium) and SLH-DSA (formerly SPHINCS+) were chosen as digital signature standards. ML-KEM is based on lattice problems and is well-suited for quantum-resistant key exchange in TLS handshakes. ML-DSA, also lattice-based, is being adopted for code signing and digital certificates. SLH-DSA is a hash-based signature scheme that, while producing larger signatures, provides mathematical diversity by relying on fundamentally different foundations than lattice-based approaches. Security companies in Shibuya and Setagaya wards are conducting rapid implementation verification of these new algorithms, establishing best practices for the broader market.

The Critical Risk of 'Harvest Now, Decrypt Later' Attacks

The most compelling reason to begin post-quantum migration immediately is the threat of "Harvest Now, Decrypt Later" (HNDL) attacks. In this strategy, adversaries intercept and store massive volumes of encrypted communications today, planning to decrypt them retroactively once CRQCs become available. Many security experts warn that nation-state cyber attack groups are already executing this approach at scale. Information requiring confidentiality for more than ten years — government classified documents, corporate intellectual property, medical records, long-term contract terms — faces the risk of today's intercepted data being decoded in the future. Business leaders in the Shinagawa and Meguro areas are increasingly recognizing this threat. Rather than waiting for quantum computers to become practical, organizations should develop migration plans now and begin addressing their most sensitive data communications in a phased approach.

Japan's CRYPTREC Guidelines and PQC Direction

CRYPTREC (Cryptography Research and Evaluation Committees), the body responsible for evaluating and recommending cryptographic technologies in Japan, is advancing the development of post-quantum cryptography guidelines. The CRYPTREC-managed "e-Government Recommended Cryptography List" serves as the standard for cryptographic technology selection in Japan's public sector, and evaluations of post-quantum algorithms informed by NIST's standardization are underway. As of 2026, domestic applicability assessments of ML-KEM and ML-DSA are in progress, with findings expected to be reflected in future list updates. The Ministry of Internal Affairs and Communications and the Digital Agency are also developing migration guidance, with requirements for government procurement systems being introduced incrementally. Companies in Ota and Minato wards may eventually face post-quantum cryptography readiness as an evaluation criterion during ISMS certification and Privacy Mark renewal audits. Monitoring both domestic and international developments while planning systematically is essential.

Migration Timeline: From 2026 to the Post-Quantum Era

Migration to post-quantum cryptography is not an overnight endeavor. Starting from the completion of NIST standardization, a phased transition spanning 2026 through 2035 represents the international consensus timeline. The period of 2026-2027 should serve as the "preparation phase," dedicated to cryptographic asset inventory, risk assessment, and migration plan development. From 2028 to 2030, the "initial migration phase" begins with transitioning the most sensitive systems to post-quantum algorithms. The years 2031-2035 constitute the "full migration phase," during which deployment extends to all systems and legacy cryptography is progressively retired. The U.S. government has signaled a mandate for complete post-quantum migration across all federal systems by 2035, and Japan is expected to follow a similar timeline. IT companies in Setagaya and Shibuya wards are already beginning their preparation phase activities in 2026.

Understanding Crypto-Agility and Why It Matters

The key concept enabling smooth post-quantum migration is "crypto-agility" — the ability to quickly switch the cryptographic algorithms used in a system without requiring extensive code changes or system downtime. Looking back at cryptographic history, algorithm transitions have occurred repeatedly: the move from MD5 to SHA-2, the deprecation of SHA-1, and the upgrade from TLS 1.0/1.1 to TLS 1.3. Yet many organizations have struggled with these transitions because algorithms were hardcoded into source code and configuration files, requiring enormous effort to update. Achieving crypto-agility requires implementing a cryptographic abstraction layer that enables algorithm changes through configuration updates alone. At Oflight in Shinagawa, we recommend incorporating crypto-agility as a standard design principle in all new system development. Introducing crypto-agility into existing systems is also achievable through phased refactoring, and the investment pays dividends well beyond the quantum migration.

Impact on TLS/HTTPS, VPN, and Code Signing

Post-quantum migration affects every layer of enterprise IT infrastructure. For TLS/HTTPS, key exchange algorithms between web servers and browsers must be updated to quantum-resistant alternatives, with hybrid key exchange using ML-KEM already experimentally supported in major browsers including Chrome and Firefox. VPN connections require quantum-resistant key exchange and authentication in protocols such as IPsec and WireGuard. Code signing demands the application of ML-DSA or SLH-DSA to the digital signatures that guarantee software authenticity, preventing quantum computer-enabled forgery. S/MIME email encryption and PDF document digital signatures are also migration targets requiring attention. Companies in Minato and Meguro wards are adopting an approach of starting with hybrid TLS/HTTPS support and gradually expanding scope to other areas. During the transition period, a hybrid approach using both traditional and post-quantum cryptography in parallel is the recommended strategy.

Cryptographic Asset Inventory: Know What You Use and Where

The first step in post-quantum migration is conducting a comprehensive inventory of all cryptographic assets used within the organization. Cryptographic assets encompass all elements related to cryptographic technology: algorithms, keys, digital certificates, encrypted communication protocols, and hash functions. Specifically, organizations should catalog TLS certificate types and expiration dates, VPN encryption methods, database encryption schemes, file server encryption configurations, email encryption protocols, and API authentication mechanisms. In many enterprises, these cryptographic assets are undocumented, leaving organizations without a clear picture of which systems use which algorithms. SMBs in Ota and Setagaya wards have found automated scanning tools effective for efficiently discovering and cataloging cryptographic assets. This inventory work serves as the critical foundation for migration prioritization and cost estimation.

Enterprise Migration Roadmap in Five Phases

We recommend a five-phase roadmap for enterprise post-quantum cryptography migration. Phase 1 (months 1-3) covers "Current State Assessment" including cryptographic asset inventory, quantum risk assessment, and stakeholder awareness building. Phase 2 (months 4-6) focuses on "Strategy Development" encompassing migration priority setting, crypto-agility policy creation, and budget planning. Phase 3 (months 7-12) involves "Pilot Migration" with validation and deployment of post-quantum cryptography on the highest-priority systems. Phase 4 (year 2) addresses "Full Deployment" with organization-wide algorithm migration and hybrid cryptography operations. Phase 5 (year 3 onward) targets "Optimization and Legacy Deprecation" with progressive elimination of traditional cryptography dependencies and complete transition to post-quantum operations. At Oflight in Shinagawa, we maintain a comprehensive support framework covering every phase from initial asset inventory through complete migration.

Cost Considerations for Small and Mid-Size Businesses

For small and mid-size businesses, the cost of post-quantum migration is a major concern. However, with proper planning, the transition can proceed without excessive burden. Companies primarily using cloud services will find infrastructure-layer costs limited, as cloud providers are advancing their own post-quantum readiness. AWS, Azure, and Google Cloud have all published post-quantum migration roadmaps, with some migration occurring automatically through service updates. For custom-developed applications, updating cryptographic libraries and related code modifications represent the primary cost drivers. TLS certificate updates can be incorporated into normal renewal cycles to minimize additional costs. SMBs in Shibuya and Minato wards are increasingly allocating post-quantum readiness budgets within their annual IT investment plans, adopting phased migration approaches spanning three to five years. The most important principle is not to delay migration because of cost concerns, but to begin planning today.

Integrating PQC with Broader Security Initiatives

Post-quantum cryptography migration gains efficiency when integrated with other security enhancement initiatives rather than pursued in isolation. For example, organizations can quantum-proof their authentication infrastructure alongside Zero Trust Architecture adoption, or incorporate crypto-agility as part of cloud migration projects. Companies considering CSMA implementation can apply post-quantum cryptography to certificate management within the identity fabric layer, building a future-ready security foundation. Incorporating automated cryptographic verification checks into DevSecOps pipelines is also important for preventing legacy cryptography usage in new development. Companies in Meguro and Ota wards have begun evaluating cryptographic algorithms during annual security audits, systematically advancing their quantum readiness. Positioning post-quantum cryptography within the overall security strategy is the key to achieving efficient and effective migration.

Need Help with Post-Quantum Readiness? Contact Oflight Today

Heard that post-quantum cryptography preparation is necessary but unsure where to start? Struggling to understand what cryptographic technologies your organization currently uses? Want to know how much time and investment the migration will require? Oflight Inc., headquartered in Shinagawa, Tokyo, is your one-stop IT partner for cryptographic technology assessment, inventory, migration planning, implementation, and ongoing operational support. We have extensive experience supporting SMBs across Minato, Shibuya, Setagaya, Meguro, and Ota wards throughout the Tokyo metropolitan area. Our initial cryptographic security assessment is completely free, so please don't hesitate to get in touch. We will thoroughly investigate your cryptographic environment and propose an optimal migration plan based on risk priorities. Start preparing for the quantum era with Oflight — our expert team is ready to help you build cryptographic resilience for the future. Contact us today for your free consultation.