xor.js

// XORCipher - Super simple encryption using XOR and Base64
//
// Depends on [Underscore](http://underscorejs.org/).
//
// As a warning, this is **not** a secure encryption algorythm. It uses a very
// simplistic keystore and will be easy to crack.
//
// The Base64 algorythm is a modification of the one used in phpjs.org
// * http://phpjs.org/functions/base64_encode/
// * http://phpjs.org/functions/base64_decode/
//
// Examples
// --------
//
//     XORCipher.encode("test", "foobar");   // => "EgocFhUX"
//     XORCipher.decode("test", "EgocFhUX"); // => "foobar"
//
// Copyright © 2013 Devin Weaver <suki@tritarget.org>
//
// This program is free software. It comes without any warranty, to
// the extent permitted by applicable law. You can redistribute it
// and/or modify it under the terms of the Do What The Fuck You Want
// To Public License, Version 2, as published by Sam Hocevar. See
// http://www.wtfpl.net/ for more details.

/* jshint forin:true, noarg:true, noempty:true, eqeqeq:true, strict:true,
   undef:true, unused:true, curly:true, browser:true, indent:2, maxerr:50 */
/* global _ */
(function (exports) {
    "use strict";

    var XORCipher = {
        encode: function (key, data) {
            data = xor_encrypt(key, data);
            return b64_encode(data);
        },
        decode: function (key, data) {
            data = b64_decode(data);
            return xor_decrypt(key, data);
        }
    };

    var b64_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

    function b64_encode(data) {
        var o1, o2, o3, h1, h2, h3, h4, bits, r, i = 0, enc = "";
        if (!data) { return data; }
        do {
            o1 = data[i++];
            o2 = data[i++];
            o3 = data[i++];
            bits = o1 << 16 | o2 << 8 | o3;
            h1 = bits >> 18 & 0x3f;
            h2 = bits >> 12 & 0x3f;
            h3 = bits >> 6 & 0x3f;
            h4 = bits & 0x3f;
            enc += b64_table.charAt(h1) + b64_table.charAt(h2) + b64_table.charAt(h3) + b64_table.charAt(h4);
        } while (i < data.length);
        r = data.length % 3;
        return (r ? enc.slice(0, r - 3) : enc) + "===".slice(r || 3);
    }

    function b64_decode(data) {
        var o1, o2, o3, h1, h2, h3, h4, bits, i = 0, result = [];
        if (!data) { return data; }
        data += "";
        do {
            h1 = b64_table.indexOf(data.charAt(i++));
            h2 = b64_table.indexOf(data.charAt(i++));
            h3 = b64_table.indexOf(data.charAt(i++));
            h4 = b64_table.indexOf(data.charAt(i++));
            bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;
            o1 = bits >> 16 & 0xff;
            o2 = bits >> 8 & 0xff;
            o3 = bits & 0xff;
            result.push(o1);
            if (h3 !== 64) {
                result.push(o2);
                if (h4 !== 64) {
                    result.push(o3);
                }
            }
        } while (i < data.length);
        return result;
    }

    function keyCharAt(key, i) {
        return key.charCodeAt(Math.floor(i % key.length));
    }

    function xor_encrypt(key, data) {
        return _.map(data, function (c, i) {
            return c.charCodeAt(0) ^ keyCharAt(key, i);
        });
    }

    function xor_decrypt(key, data) {
        return _.map(data, function (c, i) {
            return String.fromCharCode(c ^ keyCharAt(key, i));
        }).join("");
    }

    exports.XORCipher = XORCipher;

})(this);