Verify this draw

How this draw was run

This winner was drawn on our live stream using a certified random number generator, with every active entry mapped to a number in range. The draw was performed on camera and archived, so the result can be watched back in full. Every entry also carries an independent timestamp recorded before the draw.

Total entries: 800 · Winning ticket: #546.

How ticket numbers are assigned

You don’t choose your ticket number (unless a competition lets you choose your own), and it isn’t simply the next number in order. When you buy, the system gives you a number using a secret shuffle that was set when the competition opened, before anyone had bought a ticket, and can’t be changed after.

Because that shuffle is secret and gives everyone a different number:

• Two people can never end up with the same number.
• Nobody, not you and not us, can guess which number a purchase will get. On this draw the number itself doesn’t decide anything anyway: the winner is picked by the draw above, which nobody can predict.
• Your number is fixed the instant you buy, and recorded straight away.

We keep the shuffle secret so no one can work out in advance which number a purchase will get, which is what stops anyone targeting a winning ticket. Every number that’s given out still appears in the competition’s entrants list, so the numbers in play are public and can’t be quietly changed later.

// 1. the key matches the fingerprint published at open:
printf '%s' 'mj60N3I4yCsEy3K3cpymWUNNjWzPpNIs5msCt29X' | sha256sum        // => ae4ab31233a2c7d5a96c0dd12c6b7e6b6c5849362331572d924fb1b713575dec

// 2. re-run the shuffle: position -> ticket number
$seed   = 'mj60N3I4yCsEy3K3cpymWUNNjWzPpNIs5msCt29X';
$domain = 800;   // the pool the numbers are shuffled within
$prf = fn($v,$r) => (int) hexdec(substr(hash('sha256', "$seed:$r:$v"), 0, 8));
$permute = function(int $pos) use ($domain, $prf) {
    $half = (int) ceil(((int) ceil(log($domain, 2))) / 2);
    $mask = (1 << $half) - 1;
    $x = $pos - 1;
    do {
        $l = ($x >> $half) & $mask; $r = $x & $mask;
        for ($i = 0; $i < 4; $i++) { $n = $l ^ ($prf($r, $i) & $mask); $l = $r; $r = $n; }
        $x = ($l << $half) | $r;
    } while ($x >= $domain);
    return $x + 1;
};
// $permute(1), $permute(2), ... are the ticket numbers, in the order they were issued.