How the draws work

1. Commit before the challenge

Before publishing a raffle or giveaway, the server creates a random 256-bit seed and publishes SHA-256 of its hexadecimal text. The seed is encrypted at rest and hidden until the draw.

2. Freeze the tickets

After the deadline for adding spins and the team's checks, the ticket list is sorted by entry ID. Each ticket contains entryId, userId and betId, in that order (a giveaway entry that needs no spin has betId null: joining is the entry). The compact JSON digest is published with the frozen list.

3. Draw without bias

ARENA_HMAC_SHA256_V1 signs “ARENA_HMAC_SHA256_V1:manifestHash:counter” with the seed bytes. The counter starts at zero. Each digest’s first four bytes form an unsigned big-endian number. Rejection sampling removes modulo bias before selecting an index.

Selected tickets are removed. When multiple wins per player are disallowed, all tickets for that player are removed. The process continues until all positions are filled or the pool is exhausted.

4. Reveal and reproduce

The seed, canonical manifest and winner order are public after finalization. The verifier uses an independent Web Crypto implementation. You can also verify exported JSON with the command line tool in this project.