Provably Fair: the Fuel and Future of Bitcoin Casinos

4 min readJun 3, 2021


Whenever you play on a Bitcoin Casino, there are a few key features that set your mind at ease, allowing you to play clearheaded. For some players is knowing the site has instant withdrawals. For others is having their crypto protected from attacks by two-factor authentication. But for all players, it’s becoming increasingly important to know they have a fair chance of winning on transparent games. That’s what provably fair is all about.

If you are a Bitcoin Casino newbie or unsure of what provably fair is or how it works, here is a quick guide on how provably fair functions and why it will become the industry standard.

Betting on anything requires a certain amount of trust in the place you are placing your money. When the betting is done on a standard physical casino, the conditions are well known to most players, but what happens when the betting is done online?

Well, your Bitcoin deserves the same care as your casino chips, so in comes the necessity of a trustless system for gambling. By now, we know that the secret for trustless systems is encryption. And encryption is precisely the core of provably fair schemes.

Where trust in online gambling sites and encryption collide

To understand how encryption ensures trustlessness, we first need to go over the concept of hashing. The hashing process in a provably fair context consists of using an algorithm to convert a code of random numbers called a seed into a different value like a key to that seed. The most common functions used in provably fair are the SHA256, Secure Hash Algorithm, and HMACSHA256. This last one is used to generate the final result of the play. The key code, called hash, results from the SHA256 function hashing — encrypting — the seed provided by the game’s server. This hash is a one-way function, so it cannot be altered or changed in any way during or after the play.

How to verify

All certified provably fair Bitcoin Casinos have a fairness section that players can go to whenever they want to verify their bets. To learn how to verify, a player needs to clearly understand these three concepts: client seed, server seed, and nonce. As we said, a seed is a random set of numbers provided by the casino’s server (server seed) and the player (client seed). The player can modify the client seed before the play, to some extent, if they feel a certain number would bring them luck. When both seeds are combined, they produce the outcome of the play. The nonce is the number assigned to each combination of the same server and client seeds. Before the bet, the player can only see the server seed hash to avoid them tampering with the result.

Fairness sections usually display the current client seed, the hashed server seed, and the nonce.

Before the bet, the casino shows a hash (SHA256) of the server seed to guarantee that the site will not replace it. To be sure that the server seed didn’t change while playing, the players need to copy both the hashed server seed and the client seed separately, play and go back to the fairness section after the play to check. It is also advisable to change the client seed whenever possible.

Some of the casinos also include open source verifiers to check the bet with an external course outside the casino, as we show in this video:

Only Provably Fair on the Horizon for Bitcoin Casinos

The choice is easy. Say you have two windows opened with two different casinos you could bet on. One of them is provably fair, and the other is not. Why would you choose to put your money in a game that operates as a black box, shuffling plays as they please without giving players a single clue of what happens after clicking play? With provably fair, you leave the fate of the trust on math and math alone.

Knowing that there is a possibility to check the authenticity of every bet, players are becoming more demanding when it comes to picking games. Another fact that will lead towards an all provably fair industry is that players are deepening their knowledge of cryptography by the minute. Soon, all casinos will need to incorporate provably fair algorithms to stay competitive.

Trust should never be taken for granted so, hopefully, one day all Bitcoin Casinos will be provably fair. In the meanwhile, it’s better to stick with those that swear by transparency.




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