Commitment (SHA-256 of the secret)
7f717bda6ad529178fd9ea6d862321d46553ee07a48442c6f45de877b7a10fca
The secret is revealed when the tournament starts.
Before registration we publish SHA-256(secret). At the start the secret is revealed and the seed order is a Fisher-Yates shuffle of the participant IDs (ascending) using HMAC-SHA256(secret, "seed:i:attempt") without modulo bias. Nobody – not even the host – can rig the seeding.