Last updated: 29 September 2026
Quick Answer: A provably fair casino is one that shows you a hash of its secret seed before you bet, so you can check results later. On Power.Win, the six PWR Originals (Blackjack, Dice, Roulette, Crash, Mines and Plinko) work this way with SHA-256. Slots and live tables are certified by their providers instead.
You’ve watched a crash multiplier bust at 1.01x three rounds in a row and wondered whether the game knew where your cash-out was set. In a game that isn’t provably fair, you can’t answer that question yourself. A provably fair casino lets you answer it, because it locks in its side of the result before you bet and hands you the key afterwards.
Three inputs do the work: a server seed the casino hides, a client seed you control, and a nonce that counts your bets from 0. The proof covers the draw, not the odds, so the house edge is exactly the same whether you check a bet or never look.
What is a provably fair casino?
A provably fair casino is an online casino whose game results you can recompute yourself, using cryptographic inputs it committed to before you placed the bet. The term describes a verification method. It isn’t a licence, a lab badge or a promise about payouts.
You’ll see the phrase “provably fair crypto casino” more often than the bare term, because the method is most common at crypto casinos. The two ideas are separate, though. Crypto is how you pay. Provably fair is maths: a hash function, two seeds and a counter.
Provably fair gambling answers one narrow question. Was this result fixed before I bet, and did it stay fixed? It doesn’t tell you whether the odds are generous. It also can’t cover games whose result comes from somewhere else, such as a physical wheel spun in a studio.
On Power.Win, six in-house games are provably fair: the PWR Originals Blackjack, Dice, Roulette, Crash, Mines and Plinko. The rest of the lobby, meaning slots and live tables from certified third party providers, is protected by a different claim. The table sets the two side by side.
| Provably fair | RNG certified | |
|---|---|---|
| Who checks the result | You, on each bet | An accredited testing lab |
| When the check happens | After your bet, once the server seed is revealed | Before release, and at any retest |
| What you can see | Seed hash, your client seed, the nonce, the revealed server seed | A certificate naming the lab and the operator |
| Can you recompute your own round | Yes | No |
| Which Power.Win games | 6 PWR Originals: Blackjack, Dice, Roulette, Crash, Mines, Plinko | Third-party slots and RNG titles |
Checked on power.win/provably-fair and power.win/rng-certificate, 29 September 2026.
How does a cryptographic commitment prove a result was not changed?
A cryptographic commitment proves a result wasn’t changed because the casino shows you a SHA-256 hash of its server seed before you bet. Swapping that seed later would produce a different hash, and you’d already be holding the original.
Think of it as a prediction sealed in an envelope and handed to you before the game starts. Power.Win’s provably fair page says the server seed is hashed as soon as it’s generated, and only the hash is shown to you.
The page describes that hash as a commitment. When you later rotate seeds, the original seed is revealed and you check that it hashes to the string you were given.
Two properties of SHA-256 make this hold. SHA-256 produces a 256-bit digest, written as 64 hexadecimal characters, according to NIST FIPS 180-4, the US federal standard that defines it.
You can’t run the hash backwards to recover the seed, so seeing the commitment early doesn’t leak your results. And you can’t practically find a second seed with the same hash, so the casino can’t quietly substitute one.
What does a SHA-256 commitment look like?
Here’s a real hash of a made-up sample seed. Paste the seed into any SHA-256 tool and you’ll get the same 64 characters.
- Sample server seed:
pwr-sample-seed-0417 - Its SHA-256 hash:
4a2e85e8392758ccac4d8df76e4587e60de87db95d39b6e00e40cb2b29fd6883
Now change one character, the final 7 to an 8:
- Altered seed:
pwr-sample-seed-0418 - Its SHA-256 hash:
f574ad40f0a7ba00e4d6957b991a3a6c64202dd383c560a3abced3dea460484f
One changed character and not a single stretch of the hash survives. That’s the whole point. A seed altered after the commitment would fail the comparison the moment you ran it. This is an illustrative seed, not a live Power.Win one.
What is a server seed, and how do client seeds and nonces fit in?
A server seed is the casino’s secret random input for your results. The client seed is your input, and the nonce is a bet counter that makes each result unique. A provably fair game combines all three to produce every outcome, so the same three values always give the same result.
What is a server seed?
The server seed is a random string the casino generates before you play and keeps hidden, showing you only its hash. On Power.Win it’s created before gameplay begins and revealed when you rotate your seeds. That reveal is what lets you test the commitment.
What is a client seed?
The client seed is the part you control. Power.Win generates one in your browser or on your device, keeps it constant through a session, and lets you replace it with your own at any time. Because the server seed was locked before your client seed existed, the casino couldn’t have picked its seed to suit yours.
What is a nonce?
The nonce is a counter that starts at 0 and rises by 1 with every bet you place on the same seed pair, according to Power.Win’s provably fair page. Without it, one server seed and one client seed would give the same result every time. With it, your first bet uses nonce 0, your fiftieth uses nonce 49, and each output differs.
How are the three inputs combined?
Power.Win’s page says it pairs SHA-256 hashing with deterministic input sequencing. It doesn’t publish a named formula there. The common industry construction is HMAC-SHA256, defined in RFC 2104 in 1997. It uses the server seed as a secret key and the client seed plus nonce as the message.
Here’s that construction on the sample seed above, with a client seed of my-client-seed:
| Message (client seed : nonce) | HMAC-SHA256 output (first 16 hex characters) |
|---|---|
| my-client-seed:0 | dd208e55f4484f3f |
| my-client-seed:1 | 00074c0b91b8c5f2 |
Each game then turns an output like this into a dice roll, a card or a multiplier using its own mapping. Same inputs, same output, on every machine. That’s what makes a result reproducible.
Checked on power.win/provably-fair, 29 September 2026.
What are the four steps to check a provably fair bet?
Checking a provably fair bet takes four steps: save the hash, play, rotate your seeds, then recompute. The full walkthrough, with a worked Dice example, lives in our guide to verifying a casino game result yourself.
- Save the server seed hash before your first bet, as a screenshot or a note on your own device.
- Place your bets. Each one records your client seed and its nonce.
- Rotate your seeds. Power.Win reveals the previous server seed.
- Recompute. Hash the revealed seed and compare it with the hash you saved, then run the seeds and nonce through a verifier to reproduce the result.
If both checks match, nobody altered that round after you bet. If the hash doesn’t match, the commitment was broken, and your saved screenshot is the evidence to send to support.
What is a provably fair calculator?
A provably fair calculator is a verifier tool. You paste in the server seed, client seed and nonce, and it recomputes the game result so you can compare it with your bet history. Power.Win’s page says you can verify in its own interface or independently with external tools.
The rule is recompute, don’t trust. A calculator run by the casino that dealt the result is convenient, but an independent one is stronger evidence. Any open-source verifier or a short script will do, because SHA-256 and HMAC-SHA256 give identical output on every computer.
There are really two checks, and they need different tools. The hash check needs nothing more than a standard SHA-256 tool. The result check needs a verifier that uses the same game mapping as the casino, which is why game-specific calculators exist.
Which games can be provably fair, and which can’t?
Any game whose result is generated in software from seeds can be provably fair. Games whose result comes from a physical wheel, a dealt shoe or a third-party studio’s server can’t be checked this way. That’s why provably fair games are mostly in-house titles like dice, crash, mines and plinko.
On Power.Win that means the six PWR Originals. Everything else in the lobby, including slots, third-party crash and plinko titles, and live tables, is certified by its provider rather than provably fair. Power.Win also publishes an RNG certificate issued by Lean Lab Company Limited, Malta, which the certificate describes as an accredited testing facility.
For the full breakdown by title, see the provably fair games list. For how certified titles are protected, read our guide to certified third-party games.
Checked on power.win/rng-certificate, 29 September 2026.
Does provably fair mean you’ll win more?
No. Provably fair proves the draw wasn’t changed, but it doesn’t change the house edge, the payouts or your chance on any single bet. A provably fair game with a 1% edge still costs you about 1% of everything you stake over a long run of bets.
Here’s a worked example. A single-zero roulette wheel paying the standard 35 to 1 on a single number has a house edge of 1/37, or 2.70%, on every bet. Place 200 bets of $5 and you’ve wagered $1,000, with an expected loss of about $27.
That holds whether you verify every spin or none. Verifying tells you those spins weren’t altered. It doesn’t turn the $27 into a profit. The edge on each bet type is set out in roulette odds explained.
So how do you win at provably fair games? The same way you win at any casino game: by chance, bet by bet, with the house edge working against you over time. No staking pattern changes that edge.
Crash is a good illustration, and the maths is in our breakdown of crash game fairness and house edge. What the proof does give you is confidence that a losing streak came from the maths, not from someone adjusting results.
Frequently Asked Questions
Why would a casino offer both provably fair games and RNG certification?
Because each covers different games. Provably fair only works where the casino generates results from seeds you can inspect, which on Power.Win means the six Originals. Third-party slots run on their providers’ servers, so an accredited lab tests them instead.
What else should you check besides provably fair?
Check the house edge, the payout rules and who runs the site, because provably fair proves the draw only. It doesn’t cover deposits, withdrawals or account checks. On the operator side, Power.Win is licensed by the Tobique Gaming Commission, licence 0000209, operated by 3-102-968317 SRL (Costa Rica).
Does provably fair need a blockchain?
No. Provably fair relies on hash functions, not a blockchain. The server seed hash is shown in the game interface, and you can check it offline with any SHA-256 tool. Paying in crypto and verifying a result are separate things that often appear together.
Is there a way to win provably fair games more often?
No. The seeds decide each result, and the house edge is the same for every player and every client seed. Changing your seed, stake or cash-out target changes which results you see, not the long-run return of 100% minus the edge.
What protects you at a live dealer table?
Live tables use real cards, wheels and dealers streamed from a studio, so there’s no seed to recompute. On Power.Win they’re certified by their providers, and you watch the physical outcome on camera. Read the rules card on each table before you place a bet.
Sources (Citations)
- National Institute of Standards and Technology, FIPS 180-4, Secure Hash Standard (SHS): defines SHA-256 and its 256-bit digest.
- Internet Engineering Task Force, RFC 2104, HMAC: Keyed-Hashing for Message Authentication (February 1997): defines the HMAC construction.
- Power.Win, Provably Fair: server seed hashing, client seed, nonce from 0, seed rotation and independent verification (checked 29 September 2026).
- Power.Win, RNG Certification: certificate issued by Lean Lab Company Limited, Malta (checked 29 September 2026).
Take the Lead, Gamble Responsibly
Checking a result is a good habit. Setting limits before you play is a better one. Power.Win’s responsible gambling tools include deposit limits (daily, weekly or monthly), self-exclusion for 3 months up to 5 years or indefinitely, and reality checks, along with links to support such as BeGambleAware.
Decide your budget first, never double up to win back a loss, and take a break when it stops being fun.