Post-Quantum Cryptography: Why the Migration Has to Start Now, Not at Q-Day

Post-quantum cryptography is the new generation of encryption designed to survive attack by quantum computers, and large organisations need to start migrating to it now, even though no quantum computer can break today’s encryption yet. That sounds paradoxical, but the logic is straightforward and urgent: the migration takes years, and adversaries are already stealing encrypted data on the assumption they will be able to decrypt it later. For any enterprise or government body holding information that must stay secret for a decade or more, the quantum threat is not a future problem. It is a present one.

Why the clock has already started

The threat that makes this urgent is known as harvest now, decrypt later. Well resourced adversaries, including nation states, are capturing encrypted data at scale today and storing it, betting that quantum computers capable of breaking current public key cryptography will arrive within the useful secrecy life of that data. Diplomatic cables, health records, intellectual property, financial data and state secrets all have confidentiality requirements measured in decades. If your data needs to stay private until 2040, the question is not whether a quantum computer exists now, but whether one will exist before 2040. Most experts think that is a serious possibility.

That reframes the timeline entirely. The relevant deadline is not the arrival of a working quantum computer, sometimes called Q-Day. It is the moment your long lived secrets are transmitted or stored using cryptography that a future machine can unwind. For a great deal of sensitive data, that moment is already in the past.

The standards are set and the deadlines are firming up

This is no longer a research topic. NIST has finalised its first post-quantum cryptography standards, based on the ML-KEM, ML-DSA and SLH-DSA algorithms, giving organisations approved, standardised replacements for the RSA and elliptic curve cryptography in use today (NIST, Migration to Post-Quantum Cryptography). With the algorithms settled, the conversation has shifted from what to adopt to how quickly organisations can migrate.

Government timelines are hardening in parallel. In the United States, federal migration to post-quantum cryptography is being accelerated for high value assets, with contractor compliance being pulled into procurement requirements, and the National Security Agency’s CNSA 2.0 suite sets a transition running toward the end of the decade (reported analysis). For any organisation that sells to government or operates critical infrastructure, these deadlines will flow through contracts and regulation well before Q-Day.

The deadline that matters is not when quantum computers arrive. It is when the data you are protecting today stops needing to be secret. For a lot of enterprise data, that is a very long time from now.

Why this is a multi-year programme, not a patch

The instinct to treat cryptography as a switch you flip is exactly what makes this dangerous to leave late. In a large organisation, cryptography is everywhere and mostly invisible: embedded in applications, hardware, network protocols, certificates, third party services and devices that may not be easy to update. A realistic enterprise migration is measured in years, and the discovery phase alone, simply mapping where cryptography lives, can take twelve to twenty four months for a large estate.

That is why the major technology providers have set internal migration targets years out rather than treating this as a near term task. The work breaks into stages that cannot be rushed:

• Inventory. Find every place cryptography is used across the estate, including in systems you do not directly control.
• Prioritise by data secrecy life. Migrate the systems protecting your longest lived, most sensitive data first, because those are most exposed to harvest now, decrypt later.
• Build crypto agility. Re-architect so algorithms can be swapped in future without another multi-year programme, because standards will continue to evolve.
• Migrate and validate, working with vendors and partners whose products and services also need to become quantum safe.

What enterprise and government leaders should do now

1. Start the cryptographic inventory this year. It is the long pole, and nothing else can be planned accurately without it.
2. Classify data by how long it must stay confidential, and use that to sequence the migration by real risk.
3. Make crypto agility an architectural principle, so you are never again locked to a single algorithm.
4. Put PQC readiness into vendor and procurement requirements, since much of your exposure sits in third party products and services.
5. Brief the board now. This is a multi-year investment with a compliance dimension, and it competes for budget, so leadership needs to understand why it cannot wait for Q-Day.

Where Jaykan fits

Jaykan helps enterprises and government organisations prepare for the post-quantum transition, starting with cryptographic discovery across the estate, then risk-based prioritisation, crypto agile architecture and a staged migration plan aligned to emerging standards and deadlines. It is part of the forward looking cyber security work we do to keep large organisations protected against threats that are coming, not just the ones already here.

If you do not yet know where cryptography lives across your organisation, a complimentary, senior led assessment is the fastest way to establish your starting point and a practical roadmap to quantum safe.

Frequently asked questions

What is post-quantum cryptography?

Post-quantum cryptography, or PQC, is a new generation of encryption and digital signature algorithms designed to withstand attacks from quantum computers. It replaces algorithms like RSA and elliptic curve cryptography, which a sufficiently powerful quantum computer could eventually break.

Do I need to act now if quantum computers cannot break encryption yet?

Yes. The threat known as harvest now, decrypt later means adversaries are already collecting encrypted data to decrypt once quantum computers are capable. Any data that must stay confidential for years is effectively at risk today, and the migration itself takes years to complete.

Which algorithms should we be moving to?

NIST has finalised its first post-quantum standards, based on the ML-KEM, ML-DSA and SLH-DSA algorithms, as the approved replacements for current public key cryptography. These are the algorithms enterprise and government migrations should be planning around.

What is the first step in a PQC migration?

A cryptographic inventory. You cannot migrate cryptography you do not know you are using, and for large organisations simply finding where cryptography lives across applications, devices and third parties can take twelve to twenty four months, which is why it must start early.