CiteSig™

The problem

The internet has no machine-readable way to distinguish a verified fact from a plausible-sounding sentence. HTML has no <verified> tag. Search engines guess. Language models hallucinate. Regulators are starting to require provenance for AI outputs, and no standard yet exists to provide it.

CiteSig™ is the missing layer: a small, open protocol that lets publishers, journalists, researchers, and AI systems attach a signed reference to any factual claim — and lets browsers, verifiers, and downstream tools check that reference at rest and at render time.

Example — inline claim

<!-- A claim, without CiteSig -->
<p>The Great Wall of China is visible from the Moon.</p>

<!-- A claim, with CiteSig -->
<p data-citesig="cs:v1:9f2a...c8e1"
   data-verdict="refuted"
   data-confidence="0.02">
  The Great Wall of China is visible from the Moon.
</p>

The data-citesig attribute references a canonical claim record. Any verifier — a browser extension, an LLM output filter, an editorial workflow — resolves it against a public registry and returns a signed verdict.

Get started

Reference implementations are published and stable. Both packages share the same test vectors as the spec.

# Install
npm install @citesig/core

// Sign a claim
import { sign, ed25519, didKeyFromEd25519PublicKey } from '@citesig/core';
import { randomBytes } from 'crypto';
const seed = randomBytes(32);
const signer = didKeyFromEd25519PublicKey(ed25519.publicKeyFromSeed(seed));
const attestation = sign({
  claim: 'The Earth orbits the Sun.',
  signer,
  sources: [{ url: 'https://nasa.gov/...' }],
  issued_at: new Date().toISOString(),
}, seed);

# Install
pip install citesig

# Sign a claim
import os
from citesig import sign, ed25519, did_key_from_ed25519_public_key
seed = os.urandom(32)
signer = did_key_from_ed25519_public_key(ed25519.public_key_from_seed(seed))
attestation = sign({
  'claim': 'The Earth orbits the Sun.',
  'signer': signer,
  'sources': [{'url': 'https://nasa.gov/...'}],
  'issued_at': '2026-09-04T20:00:00Z',
}, seed)

Verify with verify(attestation). Emit as an HTML attribute with toCompact(attestation) / to_compact(attestation). Both libraries produce byte-identical output for the same input — the same signature verifies across every language.

Design principles

• Neutral standard, not a product. The spec, the reference implementations, and the registry contract are open. Anyone can run a verifier node.
• Cryptographically grounded. Ed25519 signatures. Content-addressed claim IDs. Independently verifiable without trusting a central authority.
• Human-readable, machine-checkable. Works in HTML, JSON, Markdown, plain text, and streaming LLM outputs. Degrades gracefully when unsupported.
• Composable with existing standards. Complements C2PA (media provenance), schema.org/ClaimReview, and W3C DIDs. Fills the missing text-claim slot.

Why a standard, not a product

Most AI-trust tools score whether an answer seems correct — a probability, delivered inside a dashboard. CiteSig™ works at a different layer. It produces a cryptographic receipt that travels with the claim itself and lets anyone verify where the AI got it.

• A protocol, not a platform. Adoption is the moat, not lock-in. Like OAuth or DKIM, the value grows as more publishers and models emit signed claims.
• Cryptographic, not statistical. Verifiers return a signed verdict, not a confidence score. Proof survives the model call and can be checked years later.
• Provider-agnostic. Works with any model, any host, any surface — HTML, JSON, Markdown, streaming LLM output. Not tied to a single vendor's stack.
• Complements, does not replace. Existing quality tools can consume CiteSig verdicts as an input signal. Governance and audit teams get the provenance trail they already need.

Status

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