Provably fair lets a player check that a result was fixed before they bet and was not changed afterwards.Model#
THAI-HILO single-player (SINGLE rooms, POST /g/thai-hilo/bet): each player has one state per game and per demo/real mode — a secret server seed (64-character lower-case hex), its hash, a client seed and a nonce. It is created on the first provably-fair call or bet with clientSeed "default" and nonce 1.
Commitment: serverSeedHash = lower-case hex SHA-256 of the server seed text. Show it before the player bets; the active server seed itself is never returned.
Client seed: POST /provably-fair/client-seed replaces the client seed and resets the nonce to 0; the server seed and its hash do not change.
Nonce: each single-player bet uses the current nonce, then the nonce goes up by 1.
Roll: bytes = HMAC-SHA256(key = the server seed as text — the 64 hex characters as-is, NOT hex-decoded; message = clientSeed + ":" + nonce in decimal). Die i (i = 0, 1, 2) = floor(uint32 big-endian of bytes[4i..4i+3] / 2^32 × 6) + 1.
Rotation: POST /provably-fair/rotate reveals the current server seed (revealedServerSeed with oldServerSeedHash), replaces it with a new one and resets the nonce to 1; the client seed is kept. Bets made under a seed can only be verified after that seed has been rotated out. GET /provably-fair/server-seed returns a rotated-out seed again by its hash.
Verify: POST /provably-fair/verify-result recomputes from what FE sends (serverSeed, clientSeed, nonce) and returns the dice and the SHA-256 of the seed. FE checks the hash equals the commitment shown before the bets and the dice equal the recorded roll; nothing is looked up on the server.
LOTTO, and THAI-HILO MULTI / MULTI_CSEED rooms, have no per-player server seed: each round publishes its own seedHash when it opens and reveals the seed at settlement. A MULTI round seed is the text "{brand}{gameCode}{roomID}{unixNano}{result}_{64-hex nonce}" (the drawn result is embedded; hash = SHA-256 of that text). A MULTI_CSEED round seed combines the room server seed with the round's client-seed slots.
In MULTI_CSEED rooms of both games, the player's clientSeed and nonce are what a bet contributes when it claims a client-seed slot.
/c/g/{gameCode}/provably-fair; rotating the single-player seed is Thai Hilo's own /g/thai-hilo/provably-fair/rotate. For Lotto rounds, /g/lotto/round/provably-fair returns the round's seeds once it has settled — see Game → Lotto (หวยเฮงเฮง) → Lotto Rules → Round modes. Modified at 2026-09-30 13:51:10
