The quantum threat is not coming. For some data, it is already here.

Quantum computing tends to get discussed in the future tense — a powerful technology that will, someday, fundamentally change what is computationally possible. That framing is misleading when it comes to cryptography. The threat to encrypted data is not contingent on a quantum computer existing today. It is already active, in a form that demands attention now.

The attack is called harvest now, decrypt later. Nation-state actors and sophisticated threat groups are systematically collecting encrypted data today — intercepting traffic, exfiltrating archives, copying protected communications — with the intention of decrypting it once sufficiently powerful quantum hardware becomes available. If that data retains value in five, ten, or fifteen years, it is already at risk.

Why current encryption will not survive quantum

The security of most public-key cryptography in use today — RSA, elliptic curve, Diffie-Hellman — rests on mathematical problems that are extremely hard for classical computers to solve. Factoring large integers. Computing discrete logarithms. These are problems where the difficulty scales in a way that makes brute-force attacks impractical with any foreseeable classical hardware.

Quantum computers change this fundamentally. Shor's algorithm, running on a sufficiently powerful quantum machine, can solve these problems in polynomial time — rendering the mathematical foundations of current public-key cryptography effectively obsolete. The keys protecting your VPN connections, your certificate infrastructure, your encrypted communications: all of it relies on assumptions that quantum computing invalidates.

Symmetric encryption — AES, for instance — is more resilient, but still weakened. Grover's algorithm effectively halves the security of symmetric keys, meaning AES-128 would offer the equivalent of 64-bit security in a post-quantum world. AES-256 survives, but much of the infrastructure built around shorter key lengths does not.

"The question is not whether your current encryption will eventually be broken by quantum. It will. The question is whether the data it protects will still matter when that happens — and for most organisations, the honest answer is yes."

What post-quantum cryptography actually means

Post-quantum cryptography — PQC — refers to a new generation of cryptographic algorithms designed to be secure against both classical and quantum attacks. These algorithms do not require quantum hardware to run; they are implemented in software, on conventional infrastructure, and are designed as drop-in replacements for the algorithms they succeed.

In 2024, the US National Institute of Standards and Technology (NIST) finalised its first set of post-quantum cryptographic standards after an eight-year evaluation process. The standardised algorithms — ML-KEM for key encapsulation and ML-DSA for digital signatures, among others — are now available for implementation and are being adopted by governments and major technology vendors across the world.

This is not a distant roadmap item. It is an active migration that is already underway in the most security-conscious sectors — defence, intelligence, financial services, critical infrastructure. The EU's cybersecurity agency ENISA has published guidance recommending organisations begin their PQC transition planning now. Several EU member states have set formal timelines for migration of government systems.

The challenge is not the algorithm — it is the infrastructure

Adopting post-quantum cryptography is not simply a matter of updating a configuration file. For most organisations, the challenge is first understanding where cryptography is actually in use — a question that turns out to be surprisingly difficult to answer in complex environments.

Certificate infrastructure, TLS configurations, VPN and network security appliances, identity and authentication systems, code signing pipelines, encrypted storage — cryptography is embedded throughout the stack, often invisibly. Before an organisation can migrate to post-quantum algorithms, it needs a clear picture of its cryptographic inventory: what is in use, where, and how critical it is.

This is where Nomios's PKI and cryptography practice typically begins when working with organisations on quantum readiness. A cryptographic discovery and risk assessment establishes the baseline — which assets are most exposed, which carry data with long-term sensitivity, and where the migration effort is most urgent. From that foundation, a phased transition plan can be built that is realistic given operational constraints and existing vendor roadmaps.

Certificate lifetimes and agility

One dimension of quantum readiness that is often underestimated is certificate agility — the organisational and technical ability to rotate certificates and cryptographic keys quickly when required. Many organisations discovered during the Log4Shell and similar incidents just how difficult rapid certificate replacement can be at scale. Quantum migration will require the same capability, applied across a much broader surface.

Building cryptographic agility into your infrastructure now — automating certificate lifecycle management, reducing manual dependencies, establishing clear ownership — is valuable independently of the quantum timeline. It is also a prerequisite for any serious PQC migration programme.

Where to start

For most organisations, the right starting point is not an immediate full migration — that is neither feasible nor necessary today. It is an honest assessment of exposure: which data and systems carry the greatest long-term sensitivity, and how well protected are they likely to be as the quantum timeline advances.

From that assessment, a prioritised roadmap emerges naturally. High-sensitivity, long-lifecycle data gets addressed first. Infrastructure that is already due for refresh gets upgraded to quantum-resistant algorithms as part of the normal cycle. Vendor roadmaps are tracked and incorporated as hardware and software support matures.

Nomios supports organisations through this process — from initial discovery and risk assessment through to architecture design and implementation. The organisations that will manage this transition most smoothly are the ones that start the planning conversation now, before urgency creates pressure to cut corners.