The threat
The signatures used today by Bitcoin, Ethereum and most websites (elliptic curves, RSA) rely on mathematical problems that an ordinary computer would need billions of years to solve. A powerful enough quantum computer could solve them in hours using Shor's algorithm (1994). None exists yet, but experts advise preparing now, because changing signatures in a worldwide system takes years.
The answer: new standards
In August 2024, the US standards agency (NIST) published three standards designed to resist quantum computers:
| FIPS 203 — ML-KEM | agreeing on a secret key (lattices) |
|---|---|
| FIPS 204 — ML-DSA | digital signatures (lattices) |
| FIPS 205 — SLH-DSA | signatures built only from hash functions |
In France, ANSSI recommends not betting everything on one mathematical family, and considers SLH-DSA a conservative choice.
What NumFranc does
ML-DSA-87 for every payment
The highest level of the standard (level 5), from the very first block: no migration needed.
SLH-DSA for every release
Software releases are signed with another, hash-based mathematical family.
SHA3-512 everywhere
512-bit fingerprints keep about 256 bits of security even against a quantum computer (Grover's algorithm).
Wallet encrypted twice
AES-256 then XChaCha20, with two independent 256-bit keys derived by Argon2id.
The trade-off
Post-quantum signatures are larger (about 4.6 KB for ML-DSA-87, versus 64 bytes for Bitcoin). NumFranc transactions are therefore heavier: a deliberate choice for long-term security.
NumFranc aims to become a leading post-quantum payment infrastructure, used by individuals and businesses alike. Open-source software under development: no NFR for sale, no promise of value.