Happy Halloween

Winners

How it works

When the giveaway is launched, the list of participants is frozen and the server creates a secret 32-byte seed. Only its SHA-256 hash is published, before the first spin.
From then on nothing of the draw can be changed: not the list, not the number of winners, not the seed, and no winner can be removed. The BASC team can only correct a typo or the image, and every correction is in the timeline with what it said before.
Spin n picks from the people still on the wheel: HMAC-SHA256(seed, "listHash:n:c"), first 8 bytes, modulo the people left (values that would bias the result are skipped with the next c).
With the last winner the seed is revealed: its hash must match the one published before, and every winner must come out of it. This page checks it in your browser, and anybody can check it with any SHA-256 / HMAC tool.