How draws work

1. When a raffle or giveaway opens, we pick a secret random seed and publish its SHA-256 fingerprint. Changing the seed later would change the fingerprint, so it can't be swapped.
2. When it closes, the entries are frozen (raffle tickets come from Roobet wagers; each giveaway entry counts once).
3. Entries are sorted by id. For pick k we compute HMAC-SHA256(seed, "drawId:k"), take its first 52 bits as a number between 0 and 1, multiply by the total tickets and walk the list to find the winner. That entry is removed before the next pick.
4. After the draw we reveal the seed. Anyone can repeat step 3 and get the same winners.