Verified Facts Protocol

// Verify a fact from verified-facts.json
import { verify } from '@noble/ed25519';

async function verifyFact(claim, signature, publicKey) {
  const msgHash = new Uint8Array(
    await crypto.subtle.digest('SHA-256',
      new TextEncoder().encode(claim))
  );
  const sig = Uint8Array.from(atob(signature), c => c.charCodeAt(0));
  const pub = Uint8Array.from(atob(publicKey), c => c.charCodeAt(0));
  return verify(sig, msgHash, pub);
}

// Usage:
const url = 'https://example.com/.well-known/verified-facts.json';
const data = await fetch(url).then(r => r.json());
for (const fact of data.facts) {
  const valid = await verifyFact(
    fact.claim, fact.signature, data.publicKey.value
  );
  console.log(fact.id, valid ? '✓' : '✗', fact.claim);
}