Post-quantum signatures for records that must last 30 years

An airworthiness or life-limited-part record can be relied on for thirty years or more. The digital signatures used to protect electronic records today, RSA and elliptic-curve signatures, are the ones that standards bodies now plan to retire because a large enough quantum computer could forge them. The two timelines overlap, and the overlap is where the risk sits.

What actually breaks: forgery, not secrecy

Most writing on quantum risk is about encryption and "harvest now, decrypt later": record encrypted traffic today, read it once a quantum computer exists. Signatures fail differently. The UK National Cyber Security Centre puts it this way: "an adversary in possession of a CRQC could forge signatures to impersonate the legitimate private key owner, or tamper with information whose authenticity is protected by a digital signature."⁵ (A CRQC is a cryptographically relevant quantum computer.)

For a maintenance record that means two things. A forger could produce a new record that verifies as if a real organisation signed it. And an old record's signature stops proving anything on its own, because a valid-looking signature could have been made by anyone. The record's data survives; its proof of origin and integrity does not.

The timeline regulators are working to

• NIST (US) published its first post-quantum signature standards in August 2024: FIPS 204 (ML-DSA, derived from CRYSTALS-Dilithium) and FIPS 205 (SLH-DSA, hash-based).^1,2 A third, FN-DSA, has not yet been published as a standard.
• NIST's draft transition plan, IR 8547, proposes that RSA and ECDSA signatures at today's common strength be "deprecated after 2030" and that RSA, ECDSA and EdDSA be "disallowed after 2035."³ It is an initial public draft, not a final rule.
• The UK NCSC sets three milestones: by 2028, define migration goals and complete discovery; by 2031, carry out the highest-priority migrations; by 2035, "complete migration to PQC of all your systems, services and products."⁴
• The EU member states' roadmap targets completion for high-risk uses by the end of 2030 and medium-risk uses by the end of 2035.⁶ Its "high-risk" test is about confidentiality, but it notes that "authenticity will also be jeopardised by quantum computers" and that long-lived PKIs need planning "well in advance."

No official body has said when a cryptographically relevant quantum computer will exist. The NCSC calls it "hard to predict."⁵ The Global Risk Institute's 2025 survey of 26 experts puts it as "quite possible (28-49%) within the next 10 years, and likely (51-70%) in the next 15."⁹ That is an expert opinion survey, not a forecast from a regulator. Either way, the window falls well inside the life of an aircraft delivered today.

Why aviation records are a special case

Most signed data only needs to be trusted for days or months. Germany's BSI notes that signatures "usually only need to be secure in the short term," but that long-lived keys need "a timely change."⁷ Aviation's status and life-limited-part records are the opposite case: they travel with the aircraft and are relied on at every sale, lease return and overhaul for decades (see how long records must be kept). FAA and EASA guidance asks for signatures that cannot be repudiated and records that stay unalterable for the whole retention period, but neither names an algorithm (see electronic signatures on maintenance records).

What protects a record that must outlive its algorithm

1. Sign new records with a post-quantum scheme

ML-DSA (FIPS 204) is the main general-purpose post-quantum signature standard. NIST describes it as "believed to be secure, even against adversaries in possession of a large-scale quantum computer."¹ One precision matters when comparing products: ML-DSA is derived from the competition entry CRYSTALS-Dilithium, but FIPS 204 changed it in several places, including a fix to "a security flaw that appeared in the third-round submission." A system that says "Dilithium3" is not necessarily implementing FIPS 204 ML-DSA-65. Ask which one.

2. Use a hybrid during the transition

A hybrid signs with both a classical and a post-quantum algorithm, so the record stays protected if either one is later found weak. NIST's draft describes hybrids as a hedge that remains secure "if at least one of the component algorithms is secure," while noting they add complexity and are expected to be temporary.³ Germany's BSI recommends hybrids where possible, and the EU roadmap recommends standardised hybrid solutions "whenever feasible and suitable."^7,6 The UK NCSC is more cautious: it says hybrid authentication "can be significantly more complex" and, for PKI, prefers a single migration to a fully post-quantum PKI.⁵ Regulators do not yet agree on this point.

3. Re-anchor old records before the old algorithms fail

Records already signed with RSA or ECDSA cannot be re-signed by people who may have left the organisation decades ago. Long-term archiving has handled this problem for years. RFC 4998, the IETF's Evidence Record Syntax, states that "during the archival period, hash algorithms and public key algorithms can become weak," and that archive timestamps "have to be renewed" before that happens.⁸ The principle: prove the record existed, unchanged, at a time when its original signature was still trustworthy, using a timestamp made with a newer, stronger algorithm. Done before a CRQC exists, that proof survives the classical signature underneath it.

Where Vextaris fits

Vextaris is a public Layer-1 blockchain, currently on testnet, that signs every transaction with a hybrid of Ed25519 and CRYSTALS-Dilithium3. Its intended role in aviation is the third step above: an independent ledger where a record's hash and signature can be anchored, so that its existence and integrity at a point in time remain provable after classical signatures can be forged. It is not a records system and does not replace one. This site asserts no aviation deployment, partnership or certification.