Provably Fair

// Example PHP code to calculate the roll
//
// Assuming you have the server seed, client seed, and nonce

$serverSeed = 'Your server seed here'; // to be generated by the server
$clientSeed = 'Your client seed here'; // can be set by the user
$nonce = 1; // this is a counter that starts at 1 and increments with each case opening

// Hash the server seed to ensure it is not tampered with
$serverHash = hash('sha256', $serverSeed); // hash of the server seed

// Calculate the roll using HMAC-SHA256
$message = "{$clientSeed}:{$nonce}";
$hash = hash_hmac('sha256', $message, $serverSeed);

// Extracting the first 8 characters of the hash
$hexPart = substr($hash, 0, 8);
$seed = hexdec($hexPart);

// Convert to a roll between 1 and 99999
$roll = ($seed % 99999) + 1;

// Your roll
echo "Roll: $roll\n";

// Items are sorted by price (most expensive first) and assigned ranges on a scale of 1-100000
// Roll values are in range [1, 99999]
// The last item's range extends to 100000 but rolls above 99999 never occur

// Example with 3 items:
Item A (rare):   15% chance (range:     1 to 15000)
Item B (mid):    35% chance (range: 15001 to 50000)
Item C (common): 50% chance (range: 50001 to 100000)

// If roll = 75123
// Item C would be selected (as 50001 ≤ 75123 ≤ 100000)

// Server seed rotation rules

1. Each server seed is used for up to 100 case openings
2. After 100 openings, a new server seed is automatically generated
3. When a server seed is revealed, a new one is generated for future openings
4. Each user has their own server seed that is used across all their openings