Server seed
A server seed is a secret random value a casino picks before you bet and uses, together with your client seed and a nonce, to work out provably fair results.
Also called hashed server seed, server seed hash
The server seed is the casino's half of a provably fair result. The casino keeps it secret while it is in use, because anyone who knew it could work out the results still to come. To prove it will not swap the seed later, the casino shows you its hash first. That hash is the commitment.
Example. Your fairness page shows a hashed server seed. You play 50 bets, then change seeds. The casino now shows the unhashed seed. You run SHA-256 on it and compare the output with the hash you saw at the start. If they match, the seed was not changed during those 50 bets. The provably fair verifier runs this check.
What people get wrong. You cannot check a bet while its server seed is still active. The seed is only revealed after you switch to a new one. And the casino picks the server seed alone. That is why your client seed matters: it adds a part the casino could not know when it made its commitment.
Some casinos hash the seed as text. Others hash the bytes that a hex seed stands for. The verifier tries both.
Related terms
- Provably fair
Provably fair is a system that lets you check for yourself that a casino fixed its part of a bet's result before you bet and did not change it afterwards.
- Client seed
A client seed is the player's input to a provably fair result, a value you can set yourself that is mixed with the casino's server seed and a nonce.
- Nonce
A nonce is a counter that goes up by one with each bet, so that every bet made with the same pair of seeds gets a different result.
- Hash
A hash is a fixed-length fingerprint of some data, where the same input always gives the same hash but the hash cannot be turned back into the input.