Quote from: TwitchySeal on Today at 07:04:18 PM

Quote from: DarkStar_ on July 03, 2020, 05:53:30 AM

Since they seem to use a unique approach to provably fair (it would have been much nicer if they just copied the standard nonce based method instead of trying to reinvent the wheel), I wrote a open source, and truly independent verifier that players can use if they want using purely client side JS. Here's an example of a verified bet.

Nice work. How did you figure out that this is what they're doing to HMac256(server, client)? Just curious since I tried and failed.

Code:

let hash = CryptoJS.HmacSHA256(serverSeed, clientSeed).toString();
   let PRNGSeed = parseInt(`0x${hash.substr(hash.length - 8)}`);
   mt.srand(PRNGSeed);
   document.getElementById("resultBox").className = "card mt-3 bg-success"
   document.getElementById("resultText").innerHTML = `Roll: ${mt.rand(0, 10000)}`;

(Not familiar with the JSMTRand package)

From the gamebetr/provable repository, we can find their PHP implementation to set the PRNG seed:

Code:

private function generateSeedInteger(): int
{
return hexdec(substr(hash_hmac('sha256', $this->getServerSeed(), $this->getClientSeed()), -8, 8));
}

Then they just use PHP's built in mt_rand method to get the random number. JSMTRand was a package I found that specifically mentioned having the same Mersenne Twister implementation as PHP, so it would generate the same random numbers given the same seed.