Quote from: BetKing Support on October 11, 2018, 01:03:19 PM

We are launching our own version of what people call Crash games, made popular by Bustabit, at https://betking.io

We use the same provably fair system as Bustabit.

I'll quote RHavar throughout this post.

Quote from: RHavar on January 23, 2018, 12:05:18 AM

Starting with a secret I've generated a chain of 10,000,000 SHA256 hashes. Each element is the hash of the lowercase, hexadecimal string representation of the previous hash.

The hash of the BetKing chain's last element is 863165db9a59e5720b3ea5659313e1f8c0546d3ef113d0959cb076cc79eec244.

Quote from: RHavar on January 23, 2018, 12:05:18 AM

Every game maps to a hash in the chain: The 10,000,000th element of the chain is the hash of game #1 and the first element in the chain is the hash of game #10,000,000. To verify that a hash belongs to a game #n, simply hash it n times and compare the result with the terminating hash.

To calculate a game's result from its hash:

Code:

const crypto = require("crypto")

function gameResult(seed, salt) {
  const nBits = 52 // number of most significant bits to use

  // 1. HMAC_SHA256(key=salt, message=seed)
  const hmac = crypto.createHmac("sha256", salt)
  hmac.update(seed)
  seed = hmac.digest("hex")

  // 2. r = 52 most significant bits
  seed = seed.slice(0, nBits/4)
  const r = parseInt(seed, 16)

  // 3. X = r / 2^52
  let X = r / Math.pow(2, nBits) // uniformly distributed in [0; 1)

  // 4. X = 99 / (1-X)
  X = 99 / (1 - X)

  // 5. return max(trunc(X), 100)
  const result = Math.floor(X)
  return Math.max(1, result / 100)
}

Before being used to calculate the corresponding result, each game hash is salted with the lowercase, hexadecimal string representation of the hash of a bitcoin block that has not been mined yet, proving that I have not deliberately picked a chain that is unfavorable for players.

The block we will use is bitcoin block 545340

Quoted for future reference. Also archived. https://archive.is/I9QXR