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A2G is a communication protocol. It does not prescribe how game servers implement RNG or determine outcomes. The operator’s certified systems are authoritative for game outcomes. These messages provide an optional transport mechanism for exposing fairness data to clients.
Servers that set capabilities.provablyFair: true in their hello message MAY include fairness proof messages in the game flow. Servers that do not support provably fair verification set capabilities.provablyFair: false and MUST NOT send these messages.
TypeDirectionDescription
seed_commitmentS → AllHash of server seed, broadcast before round
seed_revealS → AllActual seed revealed after round completion

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seed_commitment

Direction: Server → All clients (before the round begins) 
{
  type: "seed_commitment",
  gameType: string,
  tableId: string,
  handId: string,
  seedHash: string,             // SHA-256(serverSeed)
  messageId: string,
  timestamp: number
}
The server publishes a hash of the seed that will be used for this round. Since clients see the hash before playing, the server cannot change the seed after the round begins.

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seed_reveal

Direction: Server → All clients (after the round completes) 
{
  type: "seed_reveal",
  gameType: string,
  tableId: string,
  handId: string,
  seed: string,                 // The actual seed value
  algorithm: "sha256",
  messageId: string,
  timestamp: number
}

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Client Verification

After receiving seed_reveal, clients can verify that: 
SHA-256(seed) === seedHash
If the hash matches the earlier commitment, the seed was not changed after the round began. Clients can then replay the game’s RNG using the revealed seed and the algorithm described in the game specification to verify all random outcomes.

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Scope

These messages provide a transport layer for fairness data. They do not replace or override the operator’s certified RNG systems. For operators using lab-certified RNG, the fairness proof mechanism is additive — it provides an additional transparency layer without affecting how outcomes are determined. Servers that implement provably fair games MUST:
  • Broadcast seed_commitment BEFORE any outcome-determining action (dealing, spinning)
  • Reveal seeds ONLY after the round completes
  • Use a deterministic algorithm described in the game specification
  • Allow clients to verify outcomes using only the revealed seed and algorithm