What is Q-Day, and how do you prepare an AI system for it?
Q-Day is when quantum computing breaks today's encryption, and preparing an AI system means making its records post-quantum before that day arrives.
Q-Day is when a quantum computer breaks today's public-key cryptography; prepare by making records post-quantum now, because attackers already harvest encrypted data to decrypt later.
This matters now because the migration takes years and the threat does not. NIST finalised its post-quantum standards in 2024, regulators are turning to cryptographic resilience, and any organisation keeping defence, health or financial records for a decade is already inside the harvest-now-decrypt-later window. For the most sensitive data, public cloud assistants such as ChatGPT and Copilot are strong general tools, yet they cannot be the system of record, because that data cannot leave sovereign control.
What exactly is Q-Day, and has it happened yet?
Q-Day is the still-future moment a cryptographically relevant quantum computer can break RSA and elliptic-curve encryption. No credible public evidence says it has arrived yet.
The term names a threshold, not a scheduled event. When a machine can run Shor's algorithm at scale, the asymmetric cryptography that protects almost all internet traffic, signatures and stored secrets stops holding. We will not fabricate a date, because no one can name one honestly, and expert estimates keep moving. What is certain is that the transition to quantum-resistant cryptography is slow, so the work has to start well before the threshold, not on the day it is crossed.
Why does harvest now, decrypt later start the clock today?
Adversaries can copy encrypted traffic now and store it until Q-Day, then decrypt it. Any secret that must stay confidential for years is already exposed.
The confidentiality of a record is not decided when it is created; it is decided over its whole lifetime. A diplomatic cable, a patient history or a source identity that must stay sealed for fifteen years is vulnerable the moment a copy is captured, even if the key stays unbreakable for another decade. That is why the effective deadline for long-lived data is not Q-Day itself but the difference between Q-Day and how long the data must remain secret. For most regulated records, that clock started some time ago.
How do you prepare an AI system for Q-Day?
Prepare in five moves: inventory your cryptography, sign new records post-quantum, run hybrid during transition, build crypto-agility, and preserve or re-sign long-lived records.
The sequence matters. You cannot migrate what you have not catalogued, and you cannot claim resilience for records still signed with a scheme that Q-Day will break. The table below sets out each step, what it protects, and when it belongs in the programme.
| Preparation step | What it protects | When to do it |
|---|---|---|
| Inventory your cryptography | Every key, algorithm and certificate you rely on | First, before anything else |
| Sign new records with post-quantum signatures | The integrity of the audit trail | As each new record is generated |
| Run hybrid during the transition | Interoperability while standards settle | Throughout the migration |
| Build crypto-agility | Your ability to swap algorithms fast | Into the architecture, once |
| Preserve or re-sign long-lived records | Data you must keep for years | Before old signatures weaken |
Which post-quantum standards do the work, and what does each do?
Three NIST standards carry the load: FIPS 204 and FIPS 205 sign records, and FIPS 203 encapsulates keys. Signing and encapsulation are separate jobs.
FIPS 204 (ML-DSA) and FIPS 205 (SLH-DSA) are digital signature schemes: they prove a record is authentic and unaltered, which is what an audit trail depends on. FIPS 203 (ML-KEM) is key encapsulation, the mechanism for agreeing an encryption key over an untrusted channel, and it never signs anything. Confusing the two is a common design error. A Q-Day-ready system uses FIPS 204 or FIPS 205 to seal its records and FIPS 203 to protect the keys that keep data confidential.
What does a Q-Day-ready audit trail look like on a sovereign system?
It seals every action into a post-quantum signed audit ledger, running offline on operator-owned hardware, so records stay verifiable long after classical signatures fail.
Mickai is a Sovereign Intelligence Operating System, a SIOS, built and live, running offline on operator-owned hardware with every action cryptographically sealed. Its audit ledger is signed with post-quantum signatures, so a record proven today stays provable after Q-Day. A zero-egress inbound perimeter keeps data inside the estate, hardware-attested identity binds each actor to the audit chain, and offline verifiability means a seal can be re-checked without calling out to any vendor. Across 50 brains, 25 domain and 25 operational, cross-model consensus reduces single-model error before an action is sealed. The architecture is covered by 104 filed UK patent applications and 2,340 claims, owned by Mickai LTD (Companies House 17166618), filed and patent pending.
How do you keep long-lived records verifiable for decades?
Re-sign long-lived records with post-quantum signatures before old ones weaken, and keep crypto-agility so you can adopt the next standard without rebuilding the system.
Cryptography ages, and any single algorithm may one day be superseded, whether by Q-Day or by a later break. Crypto-agility means the signing scheme is a swappable component, not a load-bearing assumption welded into the design, so the estate can move to the next standard cleanly. For records that must outlive their original signatures, re-signing under a current post-quantum scheme keeps the chain of proof intact across generations of cryptography.
“The safest assumption is that data you encrypt today may be read the day quantum cryptanalysis matures, so the record has to be made post-quantum before that day, not after.”
Frequently asked questions
When will Q-Day actually happen?
No one can name the date, and we will not fabricate one. Public estimates range across the next decade and beyond, and expert opinion keeps shifting. The prudent posture is to migrate long-lived data now, because the harvest-now-decrypt-later risk does not wait for a confirmed date.
Do I need to replace all my encryption at once?
No. You run hybrid schemes that combine classical and post-quantum algorithms during the transition, so systems keep interoperating while standards settle. You prioritise long-lived and high-value data first, then work outward as tooling matures. A full rip-and-replace is neither necessary nor safe.
Which FIPS standard signs my audit records?
FIPS 204 (ML-DSA) and FIPS 205 (SLH-DSA) are the signature standards, and either can sign an audit record. FIPS 203 (ML-KEM) is key encapsulation for establishing encryption keys and never signs. Choosing the right one for each job is the core of sound post-quantum design.
Is post-quantum cryptography only a concern for AI systems?
No, it affects any system holding data that must stay confidential or verifiable for years. It matters acutely for AI systems because they concentrate sensitive records and long audit trails in one place. A sovereign system that seals every action into a post-quantum ledger keeps those trails trustworthy.
How does a sovereign AI system stay verifiable after Q-Day?
It seals every action into a post-quantum signed audit ledger running offline on operator-owned hardware, so a record proven today stays provable after classical signatures fail. Crypto-agility lets it adopt the next standard without a rebuild.