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.
Also called hash function, hash value, digest
A hash function takes any data and returns a short string of fixed length. Many crypto casinos use SHA-256 for this, which always gives 64 hex characters. Three things make it useful. The same input always gives the same output. A tiny change to the input gives a completely different output. And nobody can work back from the output to the input in any practical way.
Example. A casino picks a secret server seed and shows you its SHA-256 hash before you bet. Later it reveals the seed. You hash the seed yourself. If your result equals the hash you were shown, it is the seed the casino committed to. This is the first check in the provably fair verifier.
What people get wrong. Hashing is not encryption. Encrypted data can be decrypted with a key. A hash has no key and cannot be decoded. The only way to test a guess is to hash the guess and compare.
The word also turns up in payments. A transaction hash, or TXID, is the ID of a blockchain transaction. Paste it into a block explorer to see whether a deposit or withdrawal has been confirmed.
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.
- 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.
- 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.
- Confirmation
A confirmation is a block added to a blockchain that includes your transaction or builds on top of it, and each extra one makes the payment harder to reverse.