Is quantum computing a threat to cybersecurity today?

Not yet, in the sense that no quantum computer today can break the public-key encryption in everyday use. But the threat is real now because adversaries can copy encrypted data today and decrypt it years later. Governments therefore treat migration to quantum-resistant cryptography as a project to start now, with 2035 as the common target date.

What would a quantum computer break?

CISA states that quantum computing capable of breaking modern public-key encryption does not yet exist, and that once such machines are powerful enough they will break many widely used encryption and digital signature algorithms. The UK NCSC says quantum computers will be able to efficiently solve the hard mathematical problems that asymmetric cryptography relies on.

That points at a specific family: public-key schemes such as RSA, finite-field and elliptic curve Diffie-Hellman, and the signature schemes built on those problems. NIST's draft transition report (IR 8547) lists them for retirement: for 112-bit security strength, deprecated after 2030 and disallowed after 2035, and for 128-bit strength or more, disallowed after 2035.

Symmetric algorithms such as AES and hash-based constructions are a different class. NIST treats them separately, and the headline risk is aimed at public-key cryptography.

What is "harvest now, decrypt later"?

NIST's draft describes it directly: adversaries collect encrypted data now with the goal of decrypting it once quantum technology matures. Because sensitive data often keeps its value for many years, starting the transition now is, in NIST's words, critical. It names government secrets and medical records as examples of data with long-term sensitivity.

NIST also draws a useful distinction. Authentication does not face the same retroactive risk. An authentication system stays secure as long as the algorithms and keys are secure at the moment the authentication happens. So confidentiality of long-lived data is the urgent case, and signatures come second, though still on the migration list.

What are the official dates?

The US National Security Memorandum 10, quoted by NIST, sets 2035 as the goal for mitigating as much quantum risk as is feasible across federal systems. NIST notes timelines may vary by use case.

The NCSC gives staged milestones to organizations: by 2028, define goals, complete a discovery exercise and make an initial plan; by 2031, carry out the highest-priority migration and refine the roadmap; by 2035, complete migration of all systems, services and products. It adds that a small set of rarely used technologies may take longer.

CISA says its work with NIST, OMB and others includes helping agencies build inventories of systems vulnerable to quantum decryption.

What exists to migrate to?

In August 2024 NIST approved three post-quantum standards: FIPS 203 for key establishment, derived from CRYSTALS-Kyber, FIPS 204 for digital signatures, derived from CRYSTALS-Dilithium, and FIPS 205 for stateless hash-based signatures, derived from SPHINCS+. NIST said it is developing a further signature standard based on FALCON.

A constructed example

A hospital group stores imaging archives for thirty years and sends them between sites over a VPN that uses RSA-based key exchange. Nobody can read the traffic today. But an eavesdropper who records it now, and who gets a quantum computer in the 2030s, could read it then. For this group, the archives and transfers are at the top of the migration list, ahead of a marketing website whose pages are public anyway.

How to check or apply this

1. Build a cryptographic inventory: where public-key algorithms are used, in which libraries, protocols and certificates.
2. Rank each use by how long the protected data must stay secret.
3. Ask each supplier for its post-quantum roadmap in writing.
4. Prefer crypto agility, meaning algorithms you can swap through configuration rather than a rewrite.
5. Plan pilots of the FIPS 203, 204 and 205 algorithms in non-critical systems first.
6. Align with the NCSC dates: discovery and plan by 2028, priority migrations by 2031, complete by 2035.

Safeguard's SBOM and dependency scanning can help with step 1 at the library level, by showing which dependencies pull in cryptographic packages. It cannot see every protocol and certificate, so treat it as one input.

Quick check

Sources

• NIST, Approval of three post-quantum cryptography FIPS (August 2024)
• NIST IR 8547 (initial public draft), Transition to Post-Quantum Cryptography Standards
• NCSC, Timelines for migration to post-quantum cryptography
• CISA, Post-Quantum Cryptography Initiative

Last reviewed: 18 October 2026.