Provably fair

1. After rotating, check that SHA256(server_seed) == the hash shown to you beforehand.
2. For a case opened at a given nonce: HMAC_SHA256(server_seed, "client_seed:nonce:0").
3. First 4 bytes / 2³² = a number in [0,1). Ticket = floor(number × 100 000). The case page lists each item's ticket range; your ticket lands in exactly one.

node: crypto.createHmac("sha256", serverSeed)
  .update(clientSeed+":"+nonce+":0").digest()