3.0Cryptography
Classical vs post-quantum
What a large quantum computer would do to each kind of cryptography, in plain terms.
Broken
RSA, ECDSA on secp256k1, Ed25519 and ECDH. Shor's algorithm recovers private keys from public keys. These protect today's wallets, TLS and messengers.
Weakened
AES, SHA-2 and SHA-3. Grover's algorithm at best halves their strength; 256-bit sizes stay strong. Ethereum addresses are hashes, which is why an unused address keeps its key hidden.
Holding
ML-KEM, ML-DSA and SLH-DSA. No efficient quantum attack is known against the lattice and hash problems they use. The cost is size: kilobytes instead of tens of bytes.
Sizes side by side
| Scheme | Public key | Signature or ciphertext |
|---|---|---|
| ECDSA secp256k1 | 33 B | 65 B |
| Ed25519 | 32 B | 64 B |
| ML-DSA-44 | 1,312 B | 2,420 B |
| ML-KEM-768 | 1,184 B | 1,088 B |
| SLH-DSA-SHA2-128s | 32 B | 7,856 B |