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Crash — Provably Fair

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The three phases

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1. COMMIT — before betting opens

seed = keccak(masterPepper : roundId)      // pepper = server-only secret
hash = sha256(seed)                        // stored in crash_rounds.seed_hash

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2. PLAY — the outcome is derived from the committed seed

u = uniform(0,1) from keccak(seed : roundId)
crash = round2(clamp(0.96 / (1 − u), 1, 100))

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3. REVEAL — at settlement

1. sha256(seed) === seed_hash                      // the seed wasn't swapped
2. u = uniform(keccak(seed : roundId))             // re-derive
3. crash = round2(clamp(0.96 / (1 − u), 1, 100))   // matches the settled round

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Where to verify

• In-app: the Provably Fair popup on every game exposes the verification for the round/bet you’re looking at — same optics as the vfair games’ built-in verify.
• API: GET /api/crash?action=verify-seeds publishes (seed_hash, seed, pepper) for the 12 most recently settled bet-bearing rounds.

{
  "ok": true,
  "rounds": [
    { "roundId": 481902, "seedHash": "9f2b…", "seed": "0x81aa…", "pepper": "0x5c1e…", "crash": 1.87 }
  ]
}

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Why the pepper can’t cheat you

1. The seed hash is committed before betting opens — before the operator knows who bets or how much.
2. The seed is a deterministic function of (pepper, roundId) — the operator cannot “reroll” a round without changing the pepper, which would break every future verification (and any hash comparison against previously published rounds).
3. After reveal, sha256(seed) === seed_hash is publicly checkable — swapping the seed post-hoc is detectable by anyone.

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Odds table (what the formula implies)