function md5 (str) {
  // http://kevin.vanzonneveld.net
  // +   original by: Webtoolkit.info (http://www.webtoolkit.info/)
  // + namespaced by: Michael White (http://getsprink.com)
  // +    tweaked by: Jack
  // +   improved by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +      input by: Brett Zamir (http://brett-zamir.me)
  // +   bugfixed by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // -    depends on: utf8_encode
  // *     example 1: md5('Kevin van Zonneveld');
  // *     returns 1: '6e658d4bfcb59cc13f96c14450ac40b9'
  var xl;

  var rotateLeft = function (lValue, iShiftBits) {
    return (lValue << iShiftBits) | (lValue >>> (32 - iShiftBits));
  };

  var addUnsigned = function (lX, lY) {
    var lX4, lY4, lX8, lY8, lResult;
    lX8 = (lX & 0x80000000);
    lY8 = (lY & 0x80000000);
    lX4 = (lX & 0x40000000);
    lY4 = (lY & 0x40000000);
    lResult = (lX & 0x3FFFFFFF) + (lY & 0x3FFFFFFF);
    if (lX4 & lY4) {
      return (lResult ^ 0x80000000 ^ lX8 ^ lY8);
    }
    if (lX4 | lY4) {
      if (lResult & 0x40000000) {
        return (lResult ^ 0xC0000000 ^ lX8 ^ lY8);
      } else {
        return (lResult ^ 0x40000000 ^ lX8 ^ lY8);
      }
    } else {
      return (lResult ^ lX8 ^ lY8);
    }
  };

  var _F = function (x, y, z) {
    return (x & y) | ((~x) & z);
  };
  var _G = function (x, y, z) {
    return (x & z) | (y & (~z));
  };
  var _H = function (x, y, z) {
    return (x ^ y ^ z);
  };
  var _I = function (x, y, z) {
    return (y ^ (x | (~z)));
  };

  var _FF = function (a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(_F(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };

  var _GG = function (a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(_G(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };

  var _HH = function (a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(_H(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };

  var _II = function (a, b, c, d, x, s, ac) {
    a = addUnsigned(a, addUnsigned(addUnsigned(_I(b, c, d), x), ac));
    return addUnsigned(rotateLeft(a, s), b);
  };

  var convertToWordArray = function (str) {
    var lWordCount;
    var lMessageLength = str.length;
    var lNumberOfWords_temp1 = lMessageLength + 8;
    var lNumberOfWords_temp2 = (lNumberOfWords_temp1 - (lNumberOfWords_temp1 % 64)) / 64;
    var lNumberOfWords = (lNumberOfWords_temp2 + 1) * 16;
    var lWordArray = new Array(lNumberOfWords - 1);
    var lBytePosition = 0;
    var lByteCount = 0;
    while (lByteCount < lMessageLength) {
      lWordCount = (lByteCount - (lByteCount % 4)) / 4;
      lBytePosition = (lByteCount % 4) * 8;
      lWordArray[lWordCount] = (lWordArray[lWordCount] | (str.charCodeAt(lByteCount) << lBytePosition));
      lByteCount++;
    }
    lWordCount = (lByteCount - (lByteCount % 4)) / 4;
    lBytePosition = (lByteCount % 4) * 8;
    lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80 << lBytePosition);
    lWordArray[lNumberOfWords - 2] = lMessageLength << 3;
    lWordArray[lNumberOfWords - 1] = lMessageLength >>> 29;
    return lWordArray;
  };

  var wordToHex = function (lValue) {
    var wordToHexValue = "",
      wordToHexValue_temp = "",
      lByte, lCount;
    for (lCount = 0; lCount <= 3; lCount++) {
      lByte = (lValue >>> (lCount * 8)) & 255;
      wordToHexValue_temp = "0" + lByte.toString(16);
      wordToHexValue = wordToHexValue + wordToHexValue_temp.substr(wordToHexValue_temp.length - 2, 2);
    }
    return wordToHexValue;
  };

  var x = [],
    k, AA, BB, CC, DD, a, b, c, d, S11 = 7,
    S12 = 12,
    S13 = 17,
    S14 = 22,
    S21 = 5,
    S22 = 9,
    S23 = 14,
    S24 = 20,
    S31 = 4,
    S32 = 11,
    S33 = 16,
    S34 = 23,
    S41 = 6,
    S42 = 10,
    S43 = 15,
    S44 = 21;

  str = this.utf8_encode(str);
  x = convertToWordArray(str);
  a = 0x67452301;
  b = 0xEFCDAB89;
  c = 0x98BADCFE;
  d = 0x10325476;

  xl = x.length;
  for (k = 0; k < xl; k += 16) {
    AA = a;
    BB = b;
    CC = c;
    DD = d;
    a = _FF(a, b, c, d, x[k + 0], S11, 0xD76AA478);
    d = _FF(d, a, b, c, x[k + 1], S12, 0xE8C7B756);
    c = _FF(c, d, a, b, x[k + 2], S13, 0x242070DB);
    b = _FF(b, c, d, a, x[k + 3], S14, 0xC1BDCEEE);
    a = _FF(a, b, c, d, x[k + 4], S11, 0xF57C0FAF);
    d = _FF(d, a, b, c, x[k + 5], S12, 0x4787C62A);
    c = _FF(c, d, a, b, x[k + 6], S13, 0xA8304613);
    b = _FF(b, c, d, a, x[k + 7], S14, 0xFD469501);
    a = _FF(a, b, c, d, x[k + 8], S11, 0x698098D8);
    d = _FF(d, a, b, c, x[k + 9], S12, 0x8B44F7AF);
    c = _FF(c, d, a, b, x[k + 10], S13, 0xFFFF5BB1);
    b = _FF(b, c, d, a, x[k + 11], S14, 0x895CD7BE);
    a = _FF(a, b, c, d, x[k + 12], S11, 0x6B901122);
    d = _FF(d, a, b, c, x[k + 13], S12, 0xFD987193);
    c = _FF(c, d, a, b, x[k + 14], S13, 0xA679438E);
    b = _FF(b, c, d, a, x[k + 15], S14, 0x49B40821);
    a = _GG(a, b, c, d, x[k + 1], S21, 0xF61E2562);
    d = _GG(d, a, b, c, x[k + 6], S22, 0xC040B340);
    c = _GG(c, d, a, b, x[k + 11], S23, 0x265E5A51);
    b = _GG(b, c, d, a, x[k + 0], S24, 0xE9B6C7AA);
    a = _GG(a, b, c, d, x[k + 5], S21, 0xD62F105D);
    d = _GG(d, a, b, c, x[k + 10], S22, 0x2441453);
    c = _GG(c, d, a, b, x[k + 15], S23, 0xD8A1E681);
    b = _GG(b, c, d, a, x[k + 4], S24, 0xE7D3FBC8);
    a = _GG(a, b, c, d, x[k + 9], S21, 0x21E1CDE6);
    d = _GG(d, a, b, c, x[k + 14], S22, 0xC33707D6);
    c = _GG(c, d, a, b, x[k + 3], S23, 0xF4D50D87);
    b = _GG(b, c, d, a, x[k + 8], S24, 0x455A14ED);
    a = _GG(a, b, c, d, x[k + 13], S21, 0xA9E3E905);
    d = _GG(d, a, b, c, x[k + 2], S22, 0xFCEFA3F8);
    c = _GG(c, d, a, b, x[k + 7], S23, 0x676F02D9);
    b = _GG(b, c, d, a, x[k + 12], S24, 0x8D2A4C8A);
    a = _HH(a, b, c, d, x[k + 5], S31, 0xFFFA3942);
    d = _HH(d, a, b, c, x[k + 8], S32, 0x8771F681);
    c = _HH(c, d, a, b, x[k + 11], S33, 0x6D9D6122);
    b = _HH(b, c, d, a, x[k + 14], S34, 0xFDE5380C);
    a = _HH(a, b, c, d, x[k + 1], S31, 0xA4BEEA44);
    d = _HH(d, a, b, c, x[k + 4], S32, 0x4BDECFA9);
    c = _HH(c, d, a, b, x[k + 7], S33, 0xF6BB4B60);
    b = _HH(b, c, d, a, x[k + 10], S34, 0xBEBFBC70);
    a = _HH(a, b, c, d, x[k + 13], S31, 0x289B7EC6);
    d = _HH(d, a, b, c, x[k + 0], S32, 0xEAA127FA);
    c = _HH(c, d, a, b, x[k + 3], S33, 0xD4EF3085);
    b = _HH(b, c, d, a, x[k + 6], S34, 0x4881D05);
    a = _HH(a, b, c, d, x[k + 9], S31, 0xD9D4D039);
    d = _HH(d, a, b, c, x[k + 12], S32, 0xE6DB99E5);
    c = _HH(c, d, a, b, x[k + 15], S33, 0x1FA27CF8);
    b = _HH(b, c, d, a, x[k + 2], S34, 0xC4AC5665);
    a = _II(a, b, c, d, x[k + 0], S41, 0xF4292244);
    d = _II(d, a, b, c, x[k + 7], S42, 0x432AFF97);
    c = _II(c, d, a, b, x[k + 14], S43, 0xAB9423A7);
    b = _II(b, c, d, a, x[k + 5], S44, 0xFC93A039);
    a = _II(a, b, c, d, x[k + 12], S41, 0x655B59C3);
    d = _II(d, a, b, c, x[k + 3], S42, 0x8F0CCC92);
    c = _II(c, d, a, b, x[k + 10], S43, 0xFFEFF47D);
    b = _II(b, c, d, a, x[k + 1], S44, 0x85845DD1);
    a = _II(a, b, c, d, x[k + 8], S41, 0x6FA87E4F);
    d = _II(d, a, b, c, x[k + 15], S42, 0xFE2CE6E0);
    c = _II(c, d, a, b, x[k + 6], S43, 0xA3014314);
    b = _II(b, c, d, a, x[k + 13], S44, 0x4E0811A1);
    a = _II(a, b, c, d, x[k + 4], S41, 0xF7537E82);
    d = _II(d, a, b, c, x[k + 11], S42, 0xBD3AF235);
    c = _II(c, d, a, b, x[k + 2], S43, 0x2AD7D2BB);
    b = _II(b, c, d, a, x[k + 9], S44, 0xEB86D391);
    a = addUnsigned(a, AA);
    b = addUnsigned(b, BB);
    c = addUnsigned(c, CC);
    d = addUnsigned(d, DD);
  }

  var temp = wordToHex(a) + wordToHex(b) + wordToHex(c) + wordToHex(d);

  return temp.toLowerCase();
}