How to verify a PackLab pull
Every box is locked before it goes on sale and can be re-checked by anyone after it sells out. Here is how to check a pack yourself, in your own browser, in about five steps.
The steps
- Find your box on the verify page
Open your pack history and use “Verify this pack”, or enter the box number on the verify page. A box opens for inspection once every pack in it has sold; until then its commitments are public but the seed stays sealed.
- Check the two pre-sale fingerprints
Before the first pack sold, PackLab published a SHA-256 fingerprint of the box's complete card list and one of its secret shuffle seed. Now that the seed and the card list are revealed, your browser hashes them again and checks that both fingerprints match.
- Confirm the drand randomness round
The box named a future round of the public drand randomness beacon before it went on sale, and that pointer is inside the card-list fingerprint. The verifier fetches the round from drand's own network and confirms its value. If drand can't be reached you see an amber warning, never a silent pass.
- Replay the shuffle in your browser
Your browser mixes the revealed seed with the drand value and re-runs the same deterministic shuffle, rebuilding every pack of the box in order. Nothing in this step runs on our servers.
- Match your card
Jump to your pack number and check that the cards the replay produces are the cards you pulled. Green means every check passed; red means something doesn't match.
Start on the verify page.
Why this proves the pull was fair
The card list and the seed were fixed and fingerprinted before anyone could buy a pack, and the shuffle depends on a drand value that did not exist yet when the box was sealed. So neither the shop nor a buyer could steer which card lands in which pack. The full method is on the provably fair page.
Honest limits, and how to check without us
The verifier runs in your browser, but we serve it, and the commitments are stored by us. To check independently, use the raw drand links and the downloadable box data on each box's verify page, read where the randomness comes from on the randomness source page, and re-implement the algorithm from the published fairness specification.