Provably fair

Before you bet, the house commits to a secret server seed by publishing its SHA-256 hash. Every result is HMAC-SHA256(serverSeed, clientSeed:nonce:cursor), so neither side can steer an outcome: the house cannot change the seed after seeing your bet, and you can set the client seed. Rotate the pair at any time; the old server seed is revealed and every bet made on it can be replayed here.