Get Round Provably Fair

Returns a round's provably-fair data: the seed commitment and, after settlement, the revealed seed, the client-seed input and the drawn number, so the player can verify the draw.

Auth: Player session — Authorization: Bearer {token}
Rate limit: 300 requests per 60 s per IP (LOTTO_ROUND_PROVABLY_FAIR)
Games: LOTTO

Rules

Lotto only: the route is under /g/lotto, so system maintenance and Lotto's own maintenance window both answer 503 99915.

Body key is roundId (lower-case d). Any player in the round's currency can read it, bet or not.

Before settlement only roundId, roundCode, status, drawnAt, ticketCount and serverSeedHash are returned; drawnAt is then 0001-01-01T00:00:00Z (it is never omitted).

The room mode is not returned; infer it: nonce present = MULTI, combinedClientSeed present = MULTI_CSEED.

Verify MULTI: sha256(revealedServerSeed) == serverSeedHash, and the 5th _-separated part of revealedServerSeed == number.

Verify MULTI_CSEED: sha256(revealedServerSeed) == serverSeedHash, and number = the first 6 bytes of HMAC-SHA256(key = revealedServerSeed, msg = combinedClientSeed), each byte % 10.

A cancelled round never reveals its seed, so number / revealedServerSeed never appear for it.

baseClientSeed and ticketChain are never returned today.

A round in another currency than the session answers 404 99941, like an unknown round.

ticketCount counts every player's tickets in the round.

Validation failures answer 400 99911 with a description listing the fields, e.g. roundId is required.

Flow

Accept LOTTO only; validate roundId; check the session game.

Load the round (demo or real); it must be in the session currency.

Count the round's tickets.

Not revealed yet: return the base fields.

Revealed: add the revealed seed, the drawn number, and nonce (MULTI) or combinedClientSeed (MULTI_CSEED).

curl --location 'https://dev-api.ambfairgame.com/gapi/v1/gapi/v1/g/lotto/round/provably-fair?token=8d0c6a4e2b9f4f1c9a7e3b5d1c2e4f60' \ --header 'Authorization: Bearer 3f9a1c7e5b2d4f6081a3c5e7f9b1d3f5a7c9e1b3d5f7a9c1e3b5d7f9a1c3e5b7' \ --header 'Accept-Language: th' \ --header 'Content-Type: application/json' \ --data '{ "roundId": "tm64903fa91c2e" }'

{ "code": "0", "description": "Success.", "traceID": "0f8e2c1a-6b3d-4e5f-9a7b-1c2d3e4f5a6b", "data": { "roundId": "tm64903fa91c2e", "roundCode": "tm64903fa91c2e", "status": "settled", "drawnAt": "2026-09-30T08:15:02.117Z", "nonce": "a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3", "ticketCount": 12, "serverSeedHash": "3f04d98ae3617254171fd4f378882f775947d5e8b5218b6978401d5e832b5d1a", "revealedServerSeed": "default_LOTTO_1_1790756100123456789_482917_a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3a3", "number": "482917" } }

Request

Responses