Bitcoin Forum

 //the seed pair itself
            var clientSeed = "your client seed"; //dont forget to exclude the dash and the nonce!
            var serverSeed = "your server seed";

            //bet made with seed pair (excluding current bet)
            var nonce      = 0;

            //crypto lib for hmac function
            var crypto = require('crypto');

            var roll = function(key, text) {

                //create HMAC using server seed as key and client seed as message
                var hash = crypto.createHmac('sha512', key).update(text).digest('hex');

                var index = 0;

                var lucky = parseInt(hash.substring(index * 5, index * 5 + 5), 16);

                //keep grabbing characters from the hash while greater than 
                while (lucky >= Math.pow(10, 6)) {
                    index++;
                    lucky = parseInt(hash.substring(index * 5, index * 5 + 5), 16);

                    //if we reach the end of the hash, just default to highest number
                    if (index * 5 + 5 > 128) {
                        lucky = 99.99;
                        break;
                    }
                }

                lucky %= Math.pow(10, 4);
                lucky /= Math.pow(10, 2);

                return lucky;
            }
            console.log(roll(serverSeed, clientSeed+'-'+nonce));

Profit = Payout - Bet
0.00000395 = 0.00000495 - 0.00000100

var crypto = require('crypto');