Harvest Now, Decrypt Later

The most important quantum-security threat does not require a quantum computer to exist yet. It is called “harvest now, decrypt later”: adversaries record encrypted traffic today and archive it, betting that a future quantum computer will break it.^[1] Data with long secrecy value, state secrets, health and financial records, is therefore at risk now, which is why the response has already begun.

The West and China have chosen different tools. In August 2024, the US National Institute of Standards and Technology released its first three post-quantum cryptography (PQC) standards, new, quantum-resistant maths that runs as software on existing hardware, and urged organisations to migrate “as soon as possible.”^[2] China has instead emphasised QKD, the hardware-based approach behind its quantum network.^[3]

You don’t need a quantum computer to be a victim. Data stolen today can be decrypted tomorrow.

Why the agencies disagree

This is a genuine, unsettled debate, and a serious brief has to represent it. The US NSA and UK NCSC both decline to endorse QKD for national-security use, citing its need for special hardware, its lack of authentication, its reliance on trusted relays, and its vulnerability to simple denial-of-service, and they judge PQC more practical and cost-effective.^[3] QKD’s defenders counter that its security rests on physical law rather than unproven mathematical assumptions, and that eavesdropping is detectable; a formal rebuttal to the NSA’s objections has been published.^[4] Both points are legitimate.

The reason the threat is urgent despite the absence of a working quantum computer is arithmetic about time. Data encrypted today may still need to stay secret in ten or twenty years; if a code-breaking machine arrives inside that window, anything harvested now is exposed retroactively. That is why NIST’s “migrate as soon as possible” is not alarmism but risk management, and why the migration is already generating real spending while quantum computing itself generates almost none. The geopolitical split, software-based PQC in the West, QKD hardware plus PQC in China, means the near-term market bifurcates, and the money is in the transition, not the physics.

Our take

The migration to quantum-safe security is one of the few quantum markets generating real spending today, and it is bifurcating along geopolitical lines: PQC software in the West, QKD hardware plus PQC in China. The near-term revenue is in the transition itself, audit, migration and the crypto-agility layer, not in a bet on which physics “wins.” We treat QKD-versus-PQC as a policy and standards question to monitor, not a settled technical verdict to trade on.