What Is Provably Fair? How to Verify a Mystery Box Roll Yourself

What is provably fair?

Provably fair is a cryptographic method that lets you verify a mystery box result was decided before you opened it and was never tampered with. Instead of trusting the site, you check the math yourself. It's the single most important trust signal a mystery box site can offer.

How does provably fair work?

Three values combine to produce your result:

• Server seed — a secret random string the site generates and commits to in advance by showing you its hash, so it can't change later.
• Client seed — a value tied to you, which you can usually change.
• Nonce — a counter that increments with each open.

These are hashed together (typically with HMAC-SHA256) to produce a number that maps to your item. Because the server seed was committed up front, the site can't pick your outcome after the fact — and after rotation you can reveal the server seed and re-run the hash to confirm.

How do I verify a mystery box roll myself?

On any provably-fair site the steps are the same:

1. Note the server seed hash shown before you open.
2. Open the box and record the client seed and nonce.
3. After the server seed is revealed (on rotation), hash server seed + client seed + nonce and confirm it matches both the result and the original hash.

TroveDrops shows the server-seed hash, client seed and nonce on every open. See the TroveDrops fairness page to verify a roll, then try it on a box.

Daniel breaks down the cryptography behind provably-fair systems and shows readers how to verify an outcome themselves rather than taking a site’s word for it.