Vantri

How fairness works

Every round is decided by three things: a secret server seed, your client seed, and a nonce that counts your bets. Before you play, we show you a fingerprint (SHA‑256 hash) of the server seed. Because we can’t change the seed without changing that fingerprint, we can’t change results after you’ve bet.

When you choose Reveal seed & start new one in the game’s Fairness panel, we show you the old server seed. You can then recheck any round you played with it below.

The method for keno

  1. Bytes come from HMAC‑SHA256 with the server seed as the key and clientSeed:nonce:round as the message, where round starts at 0 and goes up when more bytes are needed.
  2. The numbers 1–40 are shuffled with a Fisher–Yates shuffle from the end of the list. Each byte is reduced to a position; bytes that would make some positions more likely are skipped.
  3. The last 10 numbers after 10 swaps are the draw.

The method for dice

  1. Bytes come from the same HMAC‑SHA256 with the server seed as the key and clientSeed:nonce:0 as the message.
  2. Four bytes at a time are read as one whole number from 0 to 4,294,967,295. Numbers of 4,294,960,000 or more are skipped, so every roll is equally likely.
  3. The roll is that number’s remainder after dividing by 10,000, so it’s a whole number from 0 to 9,999, shown as 0.00 to 99.99.
  4. Your bet uses the same nonce counter as the other games, so each bet gets its own number.

The method for limbo

  1. The first 4 bytes of HMAC‑SHA256(server seed, clientSeed:nonce:0) are read as one whole number n from 0 to 4,294,967,295.
  2. The result is 99 × 4,294,967,296 ÷ (n + 1), divided by 100 and rounded down to 2 decimals. It’s shown as at least 1.00× and at most 1,000,000×.
  3. This makes the chance of reaching any target T exactly 99 ÷ T percent.

The method for blackjack

  1. Blackjack is dealt from a 7‑deck shoe of 364 cards. Before shuffling, card k is k mod 52: 0–12 are spades A to K, 13–25 hearts, 26–38 diamonds and 39–51 clubs.
  2. The shoe is shuffled with a Fisher–Yates shuffle from the end, using HMAC‑SHA256(server seed, clientSeed:nonce:round). Each swap reads 4 bytes as a whole number and skips values that would make some positions more likely.
  3. The nonce is the one in use when the shoe was started. A new shoe is shuffled once 273 cards (75%) have been dealt, or when you change seeds.
  4. Cards are dealt in order from the shoe: your first card, the dealer’s up card, your second card, the dealer’s hidden card, then each card as it’s needed (your hits, doubles and splits first, then the dealer’s draws).
  5. You can’t change seeds while a hand is in play, so the cards still to come can’t be worked out.

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