{
  "schema_version": "lvl-knowledge-lesson-v1",
  "id": "path-x402-04-sealed-pack-integrity",
  "category": "path",
  "path_ids": [
    "build-first-x402-service"
  ],
  "title": "Sealed packs and integrity checks",
  "summary": "Payment proves you paid. Hash checks prove the files match the listing claim.",
  "body": "## Two different proofs\n\n1. **Payment verification** — chain says USDC arrived  \n2. **Content integrity** — delivered files match published `data_hash`  \n\nNeither replaces the other.\n\n## Conceptual flow\n\n1. Note listing hash (ERC-7857 style metadata)  \n2. Unlock sealed files  \n3. Canonicalize + hash  \n4. Compare; quarantine on mismatch  \n\n## What integrity does not mean\n\nA matching hash does not mean the skill is useful, safe, or continuously monitored. It means **package integrity at seal time**.\n\n## Takeaway\n\nAgents should verify content, not only payment receipts.",
  "concepts": [
    "erc-7857",
    "data-hash",
    "sealed-pack"
  ],
  "related_skills_optional": [
    {
      "skill_id": "sealed-payload-integrity-checker",
      "name": "Sealed Payload Integrity Checker",
      "price_usd": 3.99,
      "price_label": "$3.99 / unlock",
      "summary": "Verify data_hash matches delivered sealed content before trusting an unlock.",
      "outline": "https://lvlltd.com/skills/sealed-payload-integrity-checker/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=sealed-payload-integrity-checker",
      "listing": "https://lvlltd.com/listings/sealed-payload-integrity-checker/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    }
  ],
  "sort_order": 40,
  "estimated_minutes": 8,
  "last_updated": "2026-07-22T12:00:00.000Z",
  "freshness": {
    "last_updated_at": "2026-07-22T12:00:00.000Z",
    "days_since_update": 0,
    "band": "fresh",
    "score_0_100": 95,
    "label": "Fresh",
    "display": "Fresh · updated 2026-07-22 (0d ago)"
  },
  "integrity": {
    "knowledge_free": true,
    "skills_optional": true,
    "note": "This lesson is complete without purchasing any skill."
  },
  "related_bundles_optional": [],
  "url": "https://lvlltd.com/learn/lessons/path-x402-04-sealed-pack-integrity/",
  "updated_at": "2026-07-22T21:10:40.587Z"
}