HOW TO VERIFY PROVABLY FAIR DICE

Updated Jul 20268 min read

Dice is the simplest provably fair game to verify by hand — and the best place to learn how the whole system works. You bet on whether a roll between 0.00 and 100.00 will land above or below a target, and a provably fair Dice game lets you prove the number was fixed before you bet, not nudged across your threshold afterwards. This guide shows the exact formula that turns an HMAC-SHA256 hash into a roll, walks through a real worked example you can reproduce, and links you to our free Provably Fair Verifier tool.

The Three Seeds and What Dice Verification Proves

Every provably fair Dice bet is built from three inputs. The server seed is a random string the casino generates and keeps secret during play — but it commits to it in advance by publishing its SHA-256 hash, like a sealed envelope. The client seed is yours; you can set it to any value, which guarantees the casino could not have pre-selected a roll. The nonce is a counter that increases by one with every bet on that seed pair.

For Dice specifically, verification proves one thing precisely: the roll was fixed before you placed your bet, and was not nudged across your win/loss threshold afterwards. Because the server seed hash was published before the round and you chose the client seed, neither side can change the number once the bet is locked. After you rotate (retire) the seed pair, the casino reveals the unhashed server seed and you can recompute every roll. For the general mechanics across all games, see our complete guide to verifying provably fair results.

How the Hash Becomes a Roll: The Real Formula

Dice on Stake — the operator that popularised this method and publishes the algorithm openly — converts an HMAC-SHA256 hash into a roll with a short, exact chain. The same logic is implemented in the widely used open-source reference verifier lucasholder/fair, which is explicitly built to match Stake's output. Here are the steps:

• 1
  Build the HMAC. The server seed is the HMAC key; the message is the string clientSeed:nonce:cursor. Computing HMAC_SHA256(serverSeed, "clientSeed:nonce:cursor") produces a 32-byte hash (64 hex characters). For a single dice roll the cursor is 0.
• 2
  Take 4 bytes, make a float. The first 4 bytes are turned into a decimal between 0 and 1 with the formula byte₀/256¹ + byte₁/256² + byte₂/256³ + byte₃/256⁴. This spreads the value evenly across the interval [0, 1).
• 3
  Scale to the roll range. Multiply the float by 10001 and round down, then divide by 100: roll = floor(float × 10001) / 100. Stake's dice covers the inclusive range 0.00–100.00, which is exactly 10,001 distinct two-decimal outcomes — that is why the multiplier is 10001, not 10000.

That is the whole conversion. Crucially, the house edge is not in this number at all — the roll is a pure, uniform value. The edge is applied separately, through the payout multiplier the casino offers for your chosen win chance. So a perfectly fair roll and a long-run house advantage coexist, which is exactly what verification should confirm.

Worked Example You Can Reproduce

Let us derive a real roll from real inputs. These are genuine values computed with HMAC-SHA256 — paste them into any HMAC tool (or our verifier) and you will get the identical hash.

Input	Value
Server seed	serverSeed123
Client seed	clientSeed456
Nonce	1
Cursor	0

• 1
  Compute the HMAC. HMAC_SHA256("serverSeed123", "clientSeed456:1:0") =
  09a4e5c0d95150fed64b44b5029cec252ffeabc4de60292df9e70f437a1de445
• 2
  Read the first 4 bytes. The leading hex pairs are 09 a4 e5 c0, i.e. the decimal bytes 9, 164, 229, 192.
• 2
  Convert to a float. 9÷256 + 164÷256² + 229÷256³ + 192÷256⁴ = 0.03767239.
• 3
  Scale to a roll. 0.03767239 × 10001 = 376.76, floor = 376, ÷ 100 = 3.76.

Where to Find Your Dice Seeds

Before you can verify, you need the unhashed server seed, which the casino only reveals once you rotate (retire) the seed pair. Here is where to look on the main provably fair platforms:

Casino	How to Find Your Seeds
Stake	Profile icon → Settings → Fairness. Note your active client seed and the next server seed hash, then click Rotate / New Seed to reveal the previous unhashed server seed. The Dice bet detail shows the nonce.
Roobet	Open your Game History, click the Dice bet, then Fairness / Reveal Seeds. The server seed is shown after the pair is rotated, alongside the client seed and nonce.
BC.Game	Avatar → Profile → Fairness. View the current seed pair, then rotate to unhash the old server seed. Open Game History for the per-bet nonce.

What This Proves — and What It Does Not

Provably fair verification is powerful, but it is precise about what it guarantees. Be clear on both sides:

• ✓It proves the roll was not altered after your bet. The number was committed by the server seed hash before you bet over or under, so the casino could not move it across your threshold.
• ✓It proves the casino used the seeds it claimed. A matching roll confirms the published server seed really does hash to the committed value and produces the number you saw.
• ✗It does NOT remove the house edge. The edge lives in the payout multiplier, not the roll. A fair, uniform number and a long-term mathematical edge for the casino coexist — verification confirms fairness, not profitability.
• ✗It does NOT guarantee you get paid. Provably fair maths says nothing about whether a casino will process your withdrawal or treat you fairly elsewhere. For that, choose a licensed, reputable operator — see our best provably fair casinos.

Frequently Asked Questions