Automatic draws on Pure Prizes pick the winning ticket with a cryptographically secure random number generator (PHP random_int), which gives every ticket exactly the same chance (no modulo bias). The moment a winner is drawn we save a record of the draw (competition, time, number of entries, winning ticket, winner, how it was drawn, the random number used and a random salt) and publish its SHA-256 fingerprint: the Public Proof Hash. Each record also includes the hash of the draw before it, so the records form a chain. If anyone changed a record later, its hash would no longer match and the chain would break.