Provably fair (definition and limits)

Provably fair is a method, used mostly by crypto casinos, that lets a player check after the fact that a game result was fixed before they bet and was not changed. It relies on publishing a cryptographic hash of a secret before play and revealing the secret afterwards.

The phrase is easy to misread. It proves a result was not tampered with. It does not prove that the game's odds are generous.

How the scheme works

1. Commit. Before you bet, the operator shows you the hash of a secret server seed. Because a hash is fixed, the operator cannot later swap in a different seed without the hash changing.
2. Add your input. You supply a client seed, so the operator cannot have worked out the result in advance.
3. Count. A nonce, a number that goes up by one with each bet, makes every result unique.
4. Generate. The server seed, client seed and nonce are run through a keyed hash such as HMAC-SHA256, and the output is converted into the game result.
5. Reveal and check. After the round, or when you change seeds, the operator reveals the server seed. You hash it, compare it with the earlier commitment, and recompute the result yourself.

What it proves and what it does not

It proves the operator did not alter a result after seeing your bet. It does not prove the game is a good deal. A provably fair game can still have a house edge of 1 percent or 10 percent, and the checking is technical enough that most players never do it. Seed handling matters too: if a server seed leaks before the round ends, the scheme breaks.

Cashout Arcade is not provably fair

Cashout Arcade is server-authoritative. Our servers draw every result and the app only shows it, so there is no hash for you to verify. What you can check instead is the published odds: each game's return and every prize chance are on the Odds page, and automated tests in our code compare each game's payout table with its published return. That is a different kind of trust, and we do not use the label "provably fair" for our games.

Common misconceptions

• "Provably fair means I will win more." It makes no statement about the edge. Always check the return.
• "No hash, so it must be rigged." A missing proof is not evidence of cheating, but it does mean you rely on the operator's published numbers. See Are Casino Games Rigged? How to Tell and What to Check.
• "The hash chain predicts results." The hash reveals nothing about the outcome until the seeds are known.

For the longer explanation see Provably Fair Explained: Seeds, Hashes and Limits, and for how random numbers are produced see RNG (random number generator). Coins in Cashout Arcade are virtual and have no cash value.