On Sui, you can build provably-fair lotteries/raffles by leaning into its object model + consensus ordering. Here’s a compact blueprint with patterns and gotchas.

1. Shared pool object

• A Lottery shared object tracks status, deadlines, pot, commits, entries, and winners.

• All writes to it are serialized by Sui → no double-spending.

2. Ticketing pattern

• Owned tickets: mint Ticket objects per buyer.

• Sharded counters: split ticket numbering across shards for parallelism.

• Always emit events so the entry list is reconstructable.

3. Randomness

• Commit-reveal: players commit hash(salt+data), later reveal; seed = hash(all reveals + checkpoint digest).

• VRF oracle: on-chain verified VRF proof as seed.

• Mix in object version/checkpoint digest to resist bias.

4. Fairness & security

• Enforce commit/reveal deadlines.

• Seal phase: freeze entries, derive seed, draw winners, pay pot.

• Use rejection sampling or PRF stream to avoid modulo bias.

• Payments are atomic from escrow pot → no frontrunning.

5. Extras

• Refund if min entries not met.

• Optional slashing for commit-but-no-reveal.

• Emit verifiable events + deterministic winner selection so anyone can audit.

In short: use a shared lottery object, scalable ticket accounting, and commit-reveal or VRF randomness tied to checkpoint digests. Seal once, derive seed, pay winners → provably fair & race-free.