Verify a draw
Every PrizeCrate draw is provably fair. This tool recomputes the result in your own browser using the Web Crypto API — you never have to take our word for it.
1. Verify a draw result
Take the revealed seed and entry count from any winner on the winners page. We compute everything in your browser — nothing is sent to our servers.
2. Check a seed against its hash
Before a competition closes we publish the sha256 hash of the draw seed. Paste the revealed seed here and compare the output against the published drawSeedHash — if they match, the seed cannot have been changed after entries closed.
How the algorithm works
- Before the competition closes, we generate a random secret seed and publish its sha256 hash (the drawSeedHash) on the competition page. Publishing the hash first means we cannot swap the seed later — any change would produce a different hash.
- When the competition closes, all entries — paid and free postal alike — are sorted by ticket number. The total is the entry count.
- The draw computes sha256(seed + ":" + entryCount), reads the hash as a large number, and takes it modulo the entry count. That gives a winning index between 0 and entryCount − 1.
- The winneris the entry at that index in the ticket-number-ordered list. The seed, entry count, winning index and ticket number are all published in the winner’s proof.
Because the seed was committed before the close and the entry count is fixed by the entries themselves, neither we nor anyone else can steer the outcome. Anyone with a hash calculator can reproduce the result — this page is just a convenience.