Proofmode for Nostr Video (Kinds 21 & 22)

Overview

Proofmode defines a standard way to prove a Nostr video event was recorded on a real device and has not been altered. It augments NIP-71 video events on kinds 21 and 22, reuses NIP-92 imeta (including the per-variant SHA-256 x), and follows NIP conventions from NIP-01, NIP-94, and NIP-98.

When to use

• Journalism, witness, or civic video where AI/synthetic media confusion is likely.
• Any video where the audience benefits from origin + integrity proof.

Event kinds & relationship to NIP-71

Proofmode attaches to kind 21 (normal) and kind 22 (short) video events defined by NIP-71. Publishers keep using imeta for the media variants; Proofmode adds proof tags.

// NIP-71 excerpt: kinds 21/22 use imeta with url/m/dim/x...
// Proofmode tags live alongside:
["proof-version","1"],
["verification-level","verified_mobile" | "verified_web" | "basic_proof" | "unverified"],
["proof-manifest","<base64(JSON)>"],
["pgp-pubkey","<ASCII armored>"],
["pgp-fingerprint","<hex>"],
["device-attestation","<platform token>"],
["frame-hashes","<base64(JSON)>"],
["recording-segments","<int>"],
["human-interactions","<int>"]

Reference: NIP-71 kinds and use of imeta. The manifest’s media_hash must match the chosen x in the selected variant.

Tag specifications

Verification levels

Verification algorithm (client/relay)

1. Decode proof-manifest; parse JSON.
2. Import pgp-pubkey; verify pgp-fingerprint.
3. Verify OpenPGP signature over canonicalized manifest (excluding signature).
4. Match manifest.media_hash to the selected imeta variant’s x (NIP-92).
5. If present, validate device-attestation (issuer keys, freshness, package/app id, integrity flags, nonce binding).
6. Optionally sample re-hash frames and compare with frame-hashes.
7. Check segment & interaction counts vs manifest; basic timing sanity.
8. Assign level; downgrade if claim > derived.

Examples

Kind 21 with full Proofmode (verified_mobile)

{
  "kind": 21,
  "content": "Protest on Main St.",
  "tags": [
    ["title","Protest Footage"],
    ["imeta","dim 1920x1080","url https://cdn.example/v/abc.mp4","x 5c...e2","m video/mp4","image https://cdn.example/v/abc.jpg"],
    ["published_at","1736112000"],
    ["duration","120"],
    ["proof-version","1"],
    ["verification-level","verified_mobile"],
    ["proof-manifest","<base64(JSON with media_hash==imeta.x, times, signature)>"],
    ["device-attestation","<JWT>"],
    ["pgp-pubkey","-----BEGIN PGP PUBLIC KEY BLOCK-----..."],
    ["pgp-fingerprint","094F9BAE18958C238F55F793560CC828C726365F"],
    ["frame-hashes","<base64(JSON of samples)>"],
    ["recording-segments","1"],
    ["human-interactions","2"]
  ]
}

Kind 22 with web capture (verified_web)

{
  "kind": 22,
  "content": "Quick update",
  "tags": [
    ["title","Short clip"],
    ["imeta","dim 720x1280","url https://cdn.example/s/xyz.webm","x 7a...90","m video/webm"],
    ["proof-version","1"],
    ["verification-level","verified_web"],
    ["proof-manifest","<base64(JSON)>"],
    ["pgp-pubkey","-----BEGIN PGP PUBLIC KEY BLOCK-----..."],
    ["pgp-fingerprint","A1B2C3D4E5F6..."]
  ]
}

Verification (TypeScript, outline)

async function verifyProofMode(ev: NostrEvent) {
  const t = indexTags(ev.tags);
  if (!t["proof-manifest"]) return {level:"unverified", reason:"missing manifest"};

  const manifest = JSON.parse(atob(t["proof-manifest"][0]));
  const pub = await importPGP(t["pgp-pubkey"][0]);
  if (pub.fingerprint !== t["pgp-fingerprint"][0]) return {level:"unverified", reason:"fp mismatch"};

  const {signature, ...payload} = manifest;
  const canonical = canonicalizeJSON(payload);
  if (!(await verifyPGP(signature, canonical, pub))) return {level:"unverified", reason:"bad signature"};

  const chosenImetaX = pickPrimaryImetaHash(ev.tags); // from NIP-92 imeta
  if (manifest.media_hash !== chosenImetaX) return {level:"unverified", reason:"hash mismatch"};

  let attestOK = false;
  if (t["device-attestation"]) {
    attestOK = await verifyAttestation(t["device-attestation"][0], pub);
  }
  // optional: sample frame rehash

  const derived = attestOK ? "verified_mobile" : "basic_proof"; // or "verified_web" per context
  return {level: derived, attestOK};
}

Security & Privacy

• Replay/proof reuse: bind nonces to PGP key or manifest hash; check freshness.
• Frame injection: file hash + signature prevents; frame samples add granularity.
• Attestation limits: depends on OS/device integrity; failures downgrade level.
• Crypto agility: future versions can switch hash/sig algorithms.
• Privacy: prefer per-event keys; omit location by default; note correlation risk if reusing keys.

Interoperability

• Backward-compatible: unknown tags ignored per NIP-01.
• Works with NIP-71 kinds 21/22; uses NIP-92 imeta and NIP-94 file hashes.
• Discovery via tag presence; future extensions via proof-version.

References

• NIP-71 — Video Events (kinds 21/22)
• NIP-92 — Media Attachments (imeta)
• NIP-94 — File Metadata
• NIP-01 — Basic Protocol
• NIP-98 — HTTP Auth (freshness/attestation patterns)

License: CC0.