EthChase.io - Provably Fair Seeding Event

[slimz]

Welcome to the EthChase.io Provably Fair Seeding Event!

EthChase is a licensed clone of the popular bitcoin game Bustabit, and is played with Ethereum.

This will reuse the idea posted by Ryan and used for Bustabit v1.
   

• A chain of 10 million (1e7) sha256 hashes was generated, starting with a Server Secret that has been repeatedly fed the output of sha256 hash back into itself 10 million times.
      The final hash in the chain is: 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8, by publicizing it here we are preventing any ability to pick an alternate sha256 chain.
• EthChase.io will play through that chain of hashes, in reverse order, and use the hashes to determine the crash point.
• To avoid criticism that the Server Secret used in step 1 was carefully chosen to generate lots of "bad" crash points, each hash in the chain will be salted with a client seed, which we have no control of.
      The client seed will be the block hash of an Ethereum block that hasn't yet been mined: block 6200000

The reference code (javascript) is as follows:

The method to create the hash chain is simply sha256:

Code:

function genGameHash(serverSeed) {
  return crypto.createHash('sha256').update(serverSeed).digest('hex');
}

The method to convert a game hash, mix it with the picked client seed to a money pot multiplier:

Code:

function crashPointFromHash(serverSeed, clientSeed) {
  function divisible(hash, mod) {
    // We will read in 4 hex at a time, but the first chunk might be a bit smaller
    // So ABCDEFGHIJ should be chunked like  AB CDEF GHIJ
    var val = 0;
    
    var o = hash.length % 4; 
    for (var i = o > 0 ? o - 4 : 0; i < hash.length; i += 4) {
      val = ((val << 16) + parseInt(hash.substring(i, i+4), 16)) % mod;
    }

    return val === 0;
  }

  var hash = crypto.createHmac('sha256', serverSeed).update(clientSeed).digest('hex');

  /* In 1 of 101 games the game crashes instantly. */
  if (divisible(hash, 101))
     return 0;

  /* Use the most significant 52-bit from the hash
     to calculate the crash point */
  var h = parseInt(hash.slice(0,52/4),16);
  var e = Math.pow(2,52);

  return Math.floor((100 * e - h) / (e - h));
}

The chain could be generated with code such as:

Code:

var serverSecret =  'If you knew this, you could steal all my money';
var clientSeed = '0000examplehash';

var gamesToGenerate = 1e7;

var serverSeed = serverSecret;

for (var game = gamesToGenerate; game > 0; --game) {
  serverSeed = genGameHash(serverSeed);
  console.log('Game ' +  game + ' has a crash point of ' + (crashPointFromHash(serverSeed, clientSeed) / 100).toFixed(2) +'x', '\t\tHash: ' + serverSeed);
}

var terminatingHash = genGameHash(serverSeed);

console.log('The terminating hash is: ', terminatingHash);

Using our chosen starting serverSeed, the hash terminating the chain is 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8. That is to say, the first game's hash played under the new provably fair scheme, when hashed will be 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8.

[slimz]

Here is an archive of this page as proof that it will not be edited: https://web.archive.org/web/20180822083048/https://bitcointalk.org/index.php?topic=4937001.0

[devans]

Welcome to the EthChase.io Provably Fair Seeding Event!

EthChase is a licensed clone of the popular bitcoin game Bustabit, and is played with Ethereum.

This will reuse the idea posted by Ryan and used for Bustabit v1.
   

• A chain of 10 million (1e7) sha256 hashes was generated, starting with a Server Secret that has been repeatedly fed the output of sha256 hash back into itself 10 million times.
      The final hash in the chain is: 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8, by publicizing it here we are preventing any ability to pick an alternate sha256 chain.
• EthChase.io will play through that chain of hashes, in reverse order, and use the hashes to determine the crash point.
• To avoid criticism that the Server Secret used in step 1 was carefully chosen to generate lots of "bad" crash points, each hash in the chain will be salted with a client seed, which we have no control of.
      The client seed will be the block hash of an Ethereum block that hasn't yet been mined: block 6200000

The reference code (javascript) is as follows:

The method to create the hash chain is simply sha256:

Code:

function genGameHash(serverSeed) {
  return crypto.createHash('sha256').update(serverSeed).digest('hex');
}

The method to convert a game hash, mix it with the picked client seed to a money pot multiplier:

Code:

function crashPointFromHash(serverSeed, clientSeed) {
  function divisible(hash, mod) {
    // We will read in 4 hex at a time, but the first chunk might be a bit smaller
    // So ABCDEFGHIJ should be chunked like  AB CDEF GHIJ
    var val = 0;
    
    var o = hash.length % 4; 
    for (var i = o > 0 ? o - 4 : 0; i < hash.length; i += 4) {
      val = ((val << 16) + parseInt(hash.substring(i, i+4), 16)) % mod;
    }

    return val === 0;
  }

  var hash = crypto.createHmac('sha256', serverSeed).update(clientSeed).digest('hex');

  /* In 1 of 101 games the game crashes instantly. */
  if (divisible(hash, 101))
     return 0;

  /* Use the most significant 52-bit from the hash
     to calculate the crash point */
  var h = parseInt(hash.slice(0,52/4),16);
  var e = Math.pow(2,52);

  return Math.floor((100 * e - h) / (e - h));
}

The chain could be generated with code such as:

Code:

var serverSecret =  'If you knew this, you could steal all my money';
var clientSeed = '0000examplehash';

var gamesToGenerate = 1e7;

var serverSeed = serverSecret;

for (var game = gamesToGenerate; game > 0; --game) {
  serverSeed = genGameHash(serverSeed);
  console.log('Game ' +  game + ' has a crash point of ' + (crashPointFromHash(serverSeed, clientSeed) / 100).toFixed(2) +'x', '\t\tHash: ' + serverSeed);
}

var terminatingHash = genGameHash(serverSeed);

console.log('The terminating hash is: ', terminatingHash);

Using our chosen starting serverSeed, the hash terminating the chain is 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8. That is to say, the first game's hash played under the new provably fair scheme, when hashed will be 6b811a0f7816f610564cd3738ad72e5007bd6161efaaac4ac5a6dd316a0cbaa8.

Looks good 👍

Quoting for reference. Also, I confirm that Ethereum block 6200000 has not been mined yet and the current block is 6192588 at the time of this writing.