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German B2C and B2B transactional portals run on the framework we are developing! Implementing provably fair in crash games
The online gambling world has changed. Ten years ago, players just had to trust that a digital slot machine wasn’t rigged. They looked for a license at the bottom of the footer and hoped for the best. Today, that isn’t enough.
A new generation of players has taken over the market. These are people who grew up with crypto, open-source code, and a healthy dose of skepticism. They don’t want to trust you. They want to verify you.
This is why crash games have exploded in popularity. It isn’t just about the simple mechanic of a rocket flying up and crashing. It is about transparency. The technology that powers these games is called provably fair and if you are building a crash games, you cannot succeed without it.
Implementing this isn’t just a technical task. It is a marketing necessity. Here is a deep dive into how the algorithm works, the math behind the multipliers, and how you can implement it to build a bulletproof reputation.
The logic behind the trust
Traditional Random Number Generators (RNG) are like a black box. The server picks a number, the game plays out, and the player loses or wins. Nobody knows what happened inside the box.
Provably fair changes the dynamic by using a cryptographic commitment scheme. It sounds complex, but the concept is simple. The server decides the results of the game before the game even starts. It seals that result in a digital envelope and gives it to the player. The players place their bet. After the game ends, the server opens the envelope to prove that the result inside matches what actually happened.
You are essentially proving that you didn’t change the outcome based on the player’s bet size.
The three core variables
To make this work, you need three specific pieces of data that interact with each other;
- the server seed – this is the random variable generated by your casino. In crash games, this isn’t just generated once per round. It is usually part of a pre-generated chain of millions of hashes,
- the client seed – this is the variable controlled by the player. It ensures that the casino cannot know the final outcome in advance, because the result depends on a mix of the server’s secret and the player’s input,
- the nonce – this is a simple counter. It starts at zero and goes up by one for every bet made or every round played. It keeps the cryptographic track specific to each round.
The reverse hash chain
Most crash casino games use a clever technique called a reverse hash chain. This was popularized by early crypto sites and remains the gold standard.
Imagine a deck of cards. You shuffle it once and then you play through the deck from top to bottom. The hash chain works in reverse.
You start by generating a random master seed. Then you hash it using the SHA-256 algorithm. Then you hash the result of that. You do this repeatably, often up to 10 million times.
The final hash you generate is used for the first game you ever run. Second-to-last hash is used for the second game, and so on.
This creates a verifiable timeline. Because every hash is mathematically derived from the one before it, a player can take the hash from Game #50 and hash it themselves to see if it matches the hash from Game #49. If it matches, they know for a fact that the chain was generated months ago and hasn’t been tampered with.
Calculating the crash point
Now we get to the actual math. You have your seeds, but how do you turn a long string of random characters into a multiplier like 2.45x or 100.00x? You generally follow a four-step process:
- step 1 is the HMAC function – you combine the server seed and the client seed using an HMAC-SHA256 function. This mixes the casino’s secret with the player’s input to create a 64-character hexadecimal string,
- step 2 is slicing the hash – you don’t need the whole string. You typically take the first 8 or 13 characters. This gives you enough randomness to be precise without being computationally heavy,
- step 3 converts to decimal – computers read hex, but math needs numbers. You convert that slice of characters into a standard decimal number,
- step 4 is applying the formula – this is where the magic happens. You need a formula that translates that random number into a crash multiplier while establishing a house edge. The standard industry house edge for crash games is usually 1%.
The formula often looks something like this
- take the maximum possible value of your hex slice,
- divide it by the random decimal number you generated,
- apply the 1% edge logic.
If the result is less than 1.00, the game crashes instantly. This is the instant bust that keeps the casino profitable in the long run. If the result is higher, that becomes the crash point.
Why you need a calculator
You can have the best code in the world, but it means nothing if players can’t see it. This is why a provably fair calculator is essential. This is a tool, usually hosted on a third-party website or a dedicated page on your casino, that runs the open-source code of your game.
Players copy the hash and salt from their bet history and paste it into the calculator. The calculator runs the math and tells them what the result should have been. If your game crashed at 1.99x but the calculator says 2.00x, trust is destroyed instantly.
You should provide this tool openly. Do not hide it in the terms and conditions. Put a link directly in the game interface. It shows confidence.
Common developer mistakes
Building this from scratch is tricky. There are a few traps that new developers often fall into when building crash casino games:
- changing seeds without warning – you will eventually need to change your server seed (rotate the chain). When you do this, you must announce it. You should also publish the previous active seed so players can verify the entire history of the previous chain. If you switch seeds silently, players will assume you are cherry-picking bad results,
- ignoring the client seed – some lazy implementations don’t let players change their client seed. This defeats the purpose. If the player cannot influence the randomness, they have to trust that you didn’t pick a server seed that is destined to lose. Always let players randomize their client seed,
- rounding errors – floating point math is dangerous. When calculating the multiplier, you need to be precise. A tiny rounding error might turn a 2.00x win into a 1.99x loss. Players verify these things down to the micro-decimal. Use integer math wherever possible and only convert to float at the very last step.
The business case for fairness
You might be wondering if this is worth the effort. Why not just use a certified RNG from a lab?
The audience for crash games is different. They don’t care about a PDF certificate from a testing lab in Malta. They care about the code they can see.
By implementing a robust provably fair system, you are essentially marketing your platform as cheat-proof. This attracts high-volume players who are tired of suspecting the casino is playing against them.
It also protects you. If a player goes on a losing streak and accuses you of rigging the game, you don’t have to argue. You just point to the provably fair calculator and the math. The data speaks for itself.
