Random server and client seeds are generated and you can always change your client seed. These ensure the game cannot be tampered with.
The client seed and nonce that will be used for your next roll are showed along with a SHA256 hash of the server seed.
Server seed is hashed (with SHA256) and showed to you to prove their fairness .
Server seed, client seed and nonce ( number of bets made with current seed pair ) are used to generate your roll (nounce is increased by 1 each roll).
Use this freebitco provably fair checker to controll if your bet are tampered you just need to insert Server Seed, Client Seed and Nonce: