Betabit Seeding Event

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)
}

Quoting this post so people can see what it originally was with assurances that it doesn't change.

Archived at: http://archive.is/q4hc5

Also confirming the BTC block #550900 hasn't been mined yet.

Quote from: BetaBit on November 19, 2018, 08:11:09 AM

This seeding event is using the same provably fair as Bustabit link to thread

Starting with a secret we've generated a chain of 25,000,000 SHA256 hashes. Each element is the hash of the lowercase, hexadecimal string representation of the previous hash. The hash of the chain's last element is 00f34b67b5a86ade6f94f5a3c050d5d8514e9da93ddf3d91694704f3c17f9609.

Every game maps to a hash in the chain: The 25,000,000th element of the chain is the hash of game #1 and the first element in the chain is the hash of game #25,000,000. 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 bitcoin block 550900. This block has not been mined yet, proving that I have not deliberately picked a chain that is unfavorable for players.

More information about the site will be revealed once the block is mined.