[nodejs]Hashcash example

hashcash.js

// see: http://en.wikipedia.org/wiki/Hashcash                                   

var crypto = require("crypto");

var table = "0123456789/:" + "abcdefghijklmnopqrstuvwxyz" +
    "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var next = function (array) {
    for (i = array.length - 1; i >= 0; i--) {
        if (array[i] < table.length - 1) {
            array[i] += 1;
            return true;
        } else {
            array[i] = 0;
        }
    }
    return false; // overflow                                                   
};
var toSuffix = function (array) {
    return array.map(function (v) {
        return table[v];
    }).join("");
};
var hash = function (data) {
    var alg = crypto.createHash("sha1");
    alg.update(data);
    return alg.digest("hex");
};


var find = function (data) {
    for (var l = 0; l < 25; l++) {
        var array = Array(l);
        for (var i = 0; i < l; i++) array[i] = 0;
        do {
            var challenge = data + toSuffix(array);
            var cash = hash(challenge);
            if (cash.match(/^0{5}/)) {
                console.log(cash + " " + challenge);
                return challenge;
            }
        } while (next(array));
    }
};

var data = "1:40:1303030600:[email protected]::";
find(data);
// result
// 000007767c31164bd2931d8b6941974e348c3cd7 1:40:1303030600:[email protected]::lY6