Provably Fair — Verify a Draw Yourself

The commitment, in plain terms

The whole mechanism is a cryptographic commitment: the platform publishes a hash of a secret before accepting your bet. A hash cannot be reversed, so publishing it gives nothing away in advance. But once the secret is revealed, anyone can hash it again and check it matches what was published — and because finding a different input with the same SHA-256 output is computationally out of reach, the secret cannot have been swapped after the fact. Three inputs go into a result. The server seed is the platform's secret, kept until the round is settled. The client seed is yours and can usually be changed, which matters more than it looks: without player input, a platform could pick a server seed knowing the distribution of bets in advance. The nonce is a counter that increases with each play, so the same pair of seeds never produces the same result twice.

Verifying a draw, step by step

Verification needs nothing but a SHA-256 calculator, and the order is what makes it work. The data has to be captured before you play, because afterwards there is no way to prove which hash was in force. Budget five minutes the first time.

1. Record the published hash of the server seed, and your client seed, before opening anything.
2. Play, and note the result together with the nonce value.
3. Force a seed rotation by changing your client seed. Only then does the platform reveal the previous server seed, because it is no longer needed for settlement.
4. Hash the revealed seed with SHA-256 and compare it to what you recorded in step one. They must match exactly.
5. Reproduce the outcome by combining both seeds with the nonce using the platform's published formula, then mapping the digest to an index in the prize pool. The index must point at the item you received.

Four things it does not prove

A verified draw tells you the round was honest. It says nothing about whether the game is worth playing. These are independent properties and conflating them is the most common mistake made with this feature.

• Not the prize distribution. A case can be perfectly verifiable and still carry an expected value far below its price. Verifiability and value are unrelated.
• Not solvency. Nothing in the mechanism speaks to whether the operator can pay out.
• Not withdrawal behaviour. Whether a payout clears in the stated time is tested empirically, not cryptographically.
• Not legality where you live. Jurisdiction is a separate question with a separate answer.

So treat provably fair as necessary but not sufficient: its absence should disqualify a platform, its presence should not by itself qualify one. The other checks that need running are on best CS2 case opening sites.