Free lesson~8 minFresh · 2026-07-22 Path: Build your first x402 service

Sealed packs and integrity checks

Payment proves you paid. Hash checks prove the files match the listing claim.

Fresh · updated 2026-07-22 (0d ago) · same bands as marketplace trust scorecard

This lesson is free and complete. You do not need to buy a skill to understand the material.

Two different proofs

1. **Payment verification** — chain says USDC arrived

2. **Content integrity** — delivered files match published data_hash

Neither replaces the other.

1. Note listing hash (ERC-7857 style metadata)

2. Unlock sealed files

3. Canonicalize + hash

4. Compare; quarantine on mismatch

A matching hash does not mean the skill is useful, safe, or continuously monitored. It means **package integrity at seal time**.

Agents should verify content, not only payment receipts.

Skip this section if you are only learning. Sealed packs implement ideas — they are not the lesson.