Provably fair: qué es y cómo funciona

In a traditional casino, you have to take the casino's word for it. In a provably fair game, you don't need to: you can use math to verify for yourself, after every single round, that the outcome wasn't tampered with.

Provably fair' translates to 'demonstrably fair'. It is neither a license nor a third-party seal. It is a cryptographic method that leaves the operator no room to alter a result after you've placed your bet.

The problem it solves

When you play online, the outcome is generated by a server you can't see. That leaves open two reasonable suspicions:

• that the server decides the result after seeing your bet;
• что сервер определяет результат уже после того, как увидит ваш ход;

Provably fair addresses both. The operator commits to the outcome before you play, you provide data that the operator doesn't control, and at the end, you receive everything needed to repeat the calculation.

The concept in a single picture: the sealed envelope

Imagine that before flipping a coin, the other person writes the result on a piece of paper, puts it in a sealed envelope, and hands it to you. You call "heads" or "tails". Then you open the envelope.

The outcome was already written down, so they couldn't change it based on what you said. And the envelope was sealed, so you couldn't see it beforehand either.

Provably fair works the exact same way, with one difference: the envelope is a hash.

The three key components

1. Server Seed

It is a long random string generated by the casino and kept secret while you play. The outcome depends on it.

Before the game starts, you aren't shown the seed itself, but rather its SHA-256 hash: a 64-character fingerprint. A hash has two properties that make it a great sealed envelope:

• It cannot be reversed: you cannot figure out the seed from the fingerprint;" (o también: "It is a one-way process: you can't deduce the seed using the fingerprint;
• Any change to the seed, no matter how small, produces a completely different fingerprint;

That hash is the commitment. If the casino were to change the seed later, the fingerprint wouldn't match and you would notice.

2. Client Seed

This is a string provided by you. You can keep the one generated by your browser or enter your own.

Its purpose is to prevent the casino from setting up a "favorable" seed: since they don't know what value you'll provide, they cannot calculate the outcome in advance.

3. Nonce

It is a counter that increments by one with every bet. Thanks to it, the same seed pair produces a different outcome each time, without needing to generate new seeds for every play.

How they combine: HMAC-SHA256

The three components are fed into a function called HMAC-SHA256. It is an open, public standard that has been used for decades to authenticate messages across the internet.

result = HMAC-SHA256(key = server_seed, message = client_seed + nonce)

The output is a 64-character hexadecimal string. Those bytes are converted into numbers, and those numbers into the game outcome: in dice, the value of the roll; in a tower game, which tiles on each row are safe.

The key is that the function is deterministic: the same inputs always yield the exact same output. That is why anyone can replicate the calculation.

The complete game round cycle

1. Phase 1 — Commitment: The casino generates the server seed and shows you its hash.
2. Your input. Your client seed is set.
3. Gameplay. You place your bet. The outcome is calculated using both seeds and the nonce.
4. Revelation. The casino provides you with the unencrypted server seed.
5. Verification. You verify two things: first, that the SHA-256 hash of the revealed server seed matches the initial hash from Step 1; second, that re-running the HMAC calculation with all three inputs yields the exact game outcome you saw.

If both match, the outcome was predetermined before your bet and no one tampered with it.

What Provably Fair guarantees—and what it doesn't

It is worth being clear about its scope, as many websites exaggerate it.

A game can be provably fair and still have a mathematical house edge. They are two different things: the edge resides in the payout table, which is public; Provably Fair proves that this paytable was applied without cheating.

Three signs of a poorly implemented Provably Fair system

1. They don't show you the hash before playing. Without prior commitment, there is nothing to verify.
2. You cannot change your client seed. If the casino chooses it, it controls both inputs.
3. They don't publish the algorithm. If they don't explain how bytes are converted into the result, you cannot repeat the calculation.

How we apply it in CaiSats.

In Towers, before every game, you see the hash of the server seed. Your client seed is yours and you can change it. The result is generated using HMAC-SHA256, and upon completion, you receive the revealed seed to verify it. The algorithm that converts the bytes into the tower tiles is documented so you can replicate the calculation outside of our site.

Frequently Asked Questions (FAQ)

Does Provably Fair mean the game has no house edge?

No. It means that the outcome was not manipulated. The house edge is built into the payouts, and it must be published.

Do I need to know how to code to verify a game round?

No. You can use an online verifier. Knowing how to code simply allows you not to rely on it.

Can the casino know what I am going to choose?

It has no effect. The outcome is fixed by the seeds and the nonce before you make your choice, and the hash you received proves it.

What is the purpose of changing my client seed?

To ensure the casino could not anticipate your contribution. Changing it also rotates the server seed.

Is it the same as a 'blockchain' game?

No. Provably Fair uses cryptography, but the calculation occurs on a server. A blockchain is not required for it to be verifiable.