Draw verification
How to check a draw.
How the draw works
Before the event, a future round of a public randomness source is chosen. When the event ends, the entry list is frozen and published. Then that round's value is released and used to pick one entry.
Check it yourself
Take the published list and the round's value, apply the published selection rule, and you get the same winner. Nobody, including GRAIL, knows the value while entries can still change.