AES Cipher function in JavaScript.

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  AES implementation in JavaScript (c) Chris Veness 2005-2011                                   */
/*   - see http://csrc.nist.gov/publications/PubsFIPS.html#197                                    */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

var Aes = {}; // Aes namespace

/**
 * AES Cipher function: encrypt 'input' state with Rijndael algorithm
 *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
 *
 * @param {Number[]} input 16-byte (128-bit) input state array
 * @param {Number[][]} w   Key schedule as 2D byte-array (Nr+1 x Nb bytes)
 * @returns {Number[]}     Encrypted output state array
 */
Aes.cipher = function (input, w) { // main Cipher function [§5.1]
  var Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
  var Nr = w.length / Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys
  var state = [
    [],
    [],
    [],
    []
  ]; // initialise 4xNb byte-array 'state' with input [§3.4]
  for (var i = 0; i < 4 * Nb; i++) state[i % 4][Math.floor(i / 4)] = input[i];

  state = Aes.addRoundKey(state, w, 0, Nb);

  for (var round = 1; round < Nr; round++) {
    state = Aes.subBytes(state, Nb);
    state = Aes.shiftRows(state, Nb);
    state = Aes.mixColumns(state, Nb);
    state = Aes.addRoundKey(state, w, round, Nb);
  }

  state = Aes.subBytes(state, Nb);
  state = Aes.shiftRows(state, Nb);
  state = Aes.addRoundKey(state, w, Nr, Nb);

  var output = new Array(4 * Nb); // convert state to 1-d array before returning [§3.4]
  for (var i = 0; i < 4 * Nb; i++) output[i] = state[i % 4][Math.floor(i / 4)];

  return output;
};

/**
 * Perform Key Expansion to generate a Key Schedule
 *
 * @param {Number[]} key Key as 16/24/32-byte array
 * @returns {Number[][]} Expanded key schedule as 2D byte-array (Nr+1 x Nb bytes)
 */
Aes.keyExpansion = function (key) { // generate Key Schedule (byte-array Nr+1 x Nb) from Key [§5.2]
  var Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
  var Nk = key.length / 4 // key length (in words): 4/6/8 for 128/192/256-bit keys
  var Nr = Nk + 6; // no of rounds: 10/12/14 for 128/192/256-bit keys
  var w = new Array(Nb * (Nr + 1));
  var temp = new Array(4);

  for (var i = 0; i < Nk; i++) {
    var r = [key[4 * i], key[4 * i + 1], key[4 * i + 2], key[4 * i + 3]];
    w[i] = r;
  }

  for (var i = Nk; i < (Nb * (Nr + 1)); i++) {
    w[i] = new Array(4);
    for (var t = 0; t < 4; t++) temp[t] = w[i - 1][t];
    if (i % Nk == 0) {
      temp = Aes.subWord(Aes.rotWord(temp));
      for (var t = 0; t < 4; t++) temp[t] ^= Aes.rCon[i / Nk][t];
    } else if (Nk > 6 && i % Nk == 4) {
      temp = Aes.subWord(temp);
    }
    for (var t = 0; t < 4; t++) w[i][t] = w[i - Nk][t] ^ temp[t];
  }

  return w;
};

/*
 * ---- remaining routines are private, not called externally ----
 */

Aes.subBytes = function (s, Nb) { // apply SBox to state S [§5.1.1]
  for (var r = 0; r < 4; r++) {
    for (var c = 0; c < Nb; c++) s[r][c] = Aes.sBox[s[r][c]];
  }
  return s;
};

Aes.shiftRows = function (s, Nb) { // shift row r of state S left by r bytes [§5.1.2]
  var t = new Array(4);
  for (var r = 1; r < 4; r++) {
    for (var c = 0; c < 4; c++) t[c] = s[r][(c + r) % Nb]; // shift into temp copy
    for (var c = 0; c < 4; c++) s[r][c] = t[c]; // and copy back
  } // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
  return s; // see asmaes.sourceforge.net/rijndael/rijndaelImplementation.pdf
};

Aes.mixColumns = function (s, Nb) { // combine bytes of each col of state S [§5.1.3]
  for (var c = 0; c < 4; c++) {
    var a = new Array(4); // 'a' is a copy of the current column from 's'
    var b = new Array(4); // 'b' is a•{02} in GF(2^8)
    for (var i = 0; i < 4; i++) {
      a[i] = s[i][c];
      b[i] = s[i][c] & 0x80 ? s[i][c] << 1 ^ 0x011b : s[i][c] << 1;

    }
    // a[n] ^ b[n] is a•{03} in GF(2^8)
    s[0][c] = b[0] ^ a[1] ^ b[1] ^ a[2] ^ a[3]; // 2*a0 + 3*a1 + a2 + a3
    s[1][c] = a[0] ^ b[1] ^ a[2] ^ b[2] ^ a[3]; // a0 * 2*a1 + 3*a2 + a3
    s[2][c] = a[0] ^ a[1] ^ b[2] ^ a[3] ^ b[3]; // a0 + a1 + 2*a2 + 3*a3
    s[3][c] = a[0] ^ b[0] ^ a[1] ^ a[2] ^ b[3]; // 3*a0 + a1 + a2 + 2*a3
  }
  return s;
};

Aes.addRoundKey = function (state, w, rnd, Nb) { // xor Round Key into state S [§5.1.4]
  for (var r = 0; r < 4; r++) {
    for (var c = 0; c < Nb; c++) state[r][c] ^= w[rnd * 4 + c][r];
  }
  return state;
};

Aes.subWord = function (w) { // apply SBox to 4-byte word w
  for (var i = 0; i < 4; i++) w[i] = Aes.sBox[w[i]];
  return w;
};

Aes.rotWord = function (w) { // rotate 4-byte word w left by one byte
  var tmp = w[0];
  for (var i = 0; i < 3; i++) w[i] = w[i + 1];
  w[3] = tmp;
  return w;
};

// sBox is pre-computed multiplicative inverse in GF(2^8) used in subBytes and keyExpansion [§5.1.1]
Aes.sBox = [0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16];

// rCon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
Aes.rCon = [
  [0x00, 0x00, 0x00, 0x00],
  [0x01, 0x00, 0x00, 0x00],
  [0x02, 0x00, 0x00, 0x00],
  [0x04, 0x00, 0x00, 0x00],
  [0x08, 0x00, 0x00, 0x00],
  [0x10, 0x00, 0x00, 0x00],
  [0x20, 0x00, 0x00, 0x00],
  [0x40, 0x00, 0x00, 0x00],
  [0x80, 0x00, 0x00, 0x00],
  [0x1b, 0x00, 0x00, 0x00],
  [0x36, 0x00, 0x00, 0x00]
];

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  AES Counter-mode implementation in JavaScript (c) Chris Veness 2005-2011                      */
/*   - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf                       */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

Aes.Ctr = {}; // Aes.Ctr namespace: a subclass or extension of Aes

/** 
 * Encrypt a text using AES encryption in Counter mode of operation
 *
 * Unicode multi-byte character safe
 *
 * @param {String} plaintext Source text to be encrypted
 * @param {String} password  The password to use to generate a key
 * @param {Number} nBits     Number of bits to be used in the key (128, 192, or 256)
 * @returns {string}         Encrypted text
 */
Aes.Ctr.encrypt = function (plaintext, password, nBits) {
  var blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
  if (!(nBits == 128 || nBits == 192 || nBits == 256)) return ''; // standard allows 128/192/256 bit keys
  plaintext = Utf8.encode(plaintext);
  password = Utf8.encode(password);
  //var t = new Date();  // timer
  // use AES itself to encrypt password to get cipher key (using plain password as source for key 
  // expansion) - gives us well encrypted key
  var nBytes = nBits / 8; // no bytes in key
  var pwBytes = new Array(nBytes);
  for (var i = 0; i < nBytes; i++) {
    pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
  }
  var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes)); // gives us 16-byte key
  key = key.concat(key.slice(0, nBytes - 16)); // expand key to 16/24/32 bytes long
  // initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A §B.2): [0-1] = millisec, 
  // [2-3] = random, [4-7] = seconds, together giving full sub-millisec uniqueness up to Feb 2106
  var counterBlock = new Array(blockSize);

  var nonce = (new Date()).getTime(); // timestamp: milliseconds since 1-Jan-1970
  var nonceMs = nonce % 1000;
  var nonceSec = Math.floor(nonce / 1000);
  var nonceRnd = Math.floor(Math.random() * 0xffff);

  for (var i = 0; i < 2; i++) counterBlock[i] = (nonceMs >>> i * 8) & 0xff;
  for (var i = 0; i < 2; i++) counterBlock[i + 2] = (nonceRnd >>> i * 8) & 0xff;
  for (var i = 0; i < 4; i++) counterBlock[i + 4] = (nonceSec >>> i * 8) & 0xff;

  // and convert it to a string to go on the front of the ciphertext
  var ctrTxt = '';
  for (var i = 0; i < 8; i++) ctrTxt += String.fromCharCode(counterBlock[i]);

  // generate key schedule - an expansion of the key into distinct Key Rounds for each round
  var keySchedule = Aes.keyExpansion(key);

  var blockCount = Math.ceil(plaintext.length / blockSize);
  var ciphertxt = new Array(blockCount); // ciphertext as array of strings
  for (var b = 0; b < blockCount; b++) {
    // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
    // done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)
    for (var c = 0; c < 4; c++) counterBlock[15 - c] = (b >>> c * 8) & 0xff;
    for (var c = 0; c < 4; c++) counterBlock[15 - c - 4] = (b / 0x100000000 >>> c * 8)

    var cipherCntr = Aes.cipher(counterBlock, keySchedule); // -- encrypt counter block --
    // block size is reduced on final block
    var blockLength = b < blockCount - 1 ? blockSize : (plaintext.length - 1) % blockSize + 1;
    var cipherChar = new Array(blockLength);

    for (var i = 0; i < blockLength; i++) { // -- xor plaintext with ciphered counter char-by-char --
      cipherChar[i] = cipherCntr[i] ^ plaintext.charCodeAt(b * blockSize + i);
      cipherChar[i] = String.fromCharCode(cipherChar[i]);
    }
    ciphertxt[b] = cipherChar.join('');
  }

  // Array.join is more efficient than repeated string concatenation in IE
  var ciphertext = ctrTxt + ciphertxt.join('');
  ciphertext = Base64.encode(ciphertext); // encode in base64
  //alert((new Date()) - t);
  return ciphertext;
};

/** 
 * Decrypt a text encrypted by AES in counter mode of operation
 *
 * @param {String} ciphertext Source text to be encrypted
 * @param {String} password   The password to use to generate a key
 * @param {Number} nBits      Number of bits to be used in the key (128, 192, or 256)
 * @returns {String}          Decrypted text
 */
Aes.Ctr.decrypt = function (ciphertext, password, nBits) {
  var blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
  if (!(nBits == 128 || nBits == 192 || nBits == 256)) return ''; // standard allows 128/192/256 bit keys
  ciphertext = Base64.decode(ciphertext);
  password = Utf8.encode(password);
  //var t = new Date();  // timer
  // use AES to encrypt password (mirroring encrypt routine)
  var nBytes = nBits / 8; // no bytes in key
  var pwBytes = new Array(nBytes);
  for (var i = 0; i < nBytes; i++) {
    pwBytes[i] = isNaN(password.charCodeAt(i)) ? 0 : password.charCodeAt(i);
  }
  var key = Aes.cipher(pwBytes, Aes.keyExpansion(pwBytes));
  key = key.concat(key.slice(0, nBytes - 16)); // expand key to 16/24/32 bytes long
  // recover nonce from 1st 8 bytes of ciphertext
  var counterBlock = new Array(8);
  ctrTxt = ciphertext.slice(0, 8);
  for (var i = 0; i < 8; i++) counterBlock[i] = ctrTxt.charCodeAt(i);

  // generate key schedule
  var keySchedule = Aes.keyExpansion(key);

  // separate ciphertext into blocks (skipping past initial 8 bytes)
  var nBlocks = Math.ceil((ciphertext.length - 8) / blockSize);
  var ct = new Array(nBlocks);
  for (var b = 0; b < nBlocks; b++) ct[b] = ciphertext.slice(8 + b * blockSize, 8 + b * blockSize + blockSize);
  ciphertext = ct; // ciphertext is now array of block-length strings
  // plaintext will get generated block-by-block into array of block-length strings
  var plaintxt = new Array(ciphertext.length);

  for (var b = 0; b < nBlocks; b++) {
    // set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
    for (var c = 0; c < 4; c++) counterBlock[15 - c] = ((b) >>> c * 8) & 0xff;
    for (var c = 0; c < 4; c++) counterBlock[15 - c - 4] = (((b + 1) / 0x100000000 - 1) >>> c * 8) & 0xff;

    var cipherCntr = Aes.cipher(counterBlock, keySchedule); // encrypt counter block
    var plaintxtByte = new Array(ciphertext[b].length);
    for (var i = 0; i < ciphertext[b].length; i++) {
      // -- xor plaintxt with ciphered counter byte-by-byte --
      plaintxtByte[i] = cipherCntr[i] ^ ciphertext[b].charCodeAt(i);
      plaintxtByte[i] = String.fromCharCode(plaintxtByte[i]);
    }
    plaintxt[b] = plaintxtByte.join('');
  }

  // join array of blocks into single plaintext string
  var plaintext = plaintxt.join('');
  plaintext = Utf8.decode(plaintext); // decode from UTF8 back to Unicode multi-byte chars
  //alert((new Date()) - t);

  return plaintext;
};

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  Base64 class: Base 64 encoding / decoding (c) Chris Veness 2002-2011                          */
/*    note: depends on Utf8 class                                                                 */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

var Base64 = {}; // Base64 namespace

Base64.code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

/**
 * Encode string into Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, no newlines are added.
 *
 * @param {String} str The string to be encoded as base-64
 * @param {Boolean} [utf8encode=false] Flag to indicate whether str is Unicode string to be encoded 
 *   to UTF8 before conversion to base64; otherwise string is assumed to be 8-bit characters
 * @returns {String} Base64-encoded string
 */
Base64.encode = function (str, utf8encode) { // http://tools.ietf.org/html/rfc4648
  utf8encode = (typeof utf8encode == 'undefined') ? false : utf8encode;
  var o1, o2, o3, bits, h1, h2, h3, h4, e = [],
    pad = '',
    c, plain, coded;
  var b64 = Base64.code;

  plain = utf8encode ? str.encodeUTF8() : str;

  c = plain.length % 3; // pad string to length of multiple of 3
  if (c > 0) {
    while (c++ < 3) {
      pad += '=';
      plain += '\0';
    }
  }
  // note: doing padding here saves us doing special-case packing for trailing 1 or 2 chars
  for (c = 0; c < plain.length; c += 3) { // pack three octets into four hexets
    o1 = plain.charCodeAt(c);
    o2 = plain.charCodeAt(c + 1);
    o3 = plain.charCodeAt(c + 2);

    bits = o1 << 16 | o2 << 8 | o3;

    h1 = bits >> 18 & 0x3f;
    h2 = bits >> 12 & 0x3f;
    h3 = bits >> 6 & 0x3f;
    h4 = bits & 0x3f;

    // use hextets to index into code string
    e[c / 3] = b64.charAt(h1) + b64.charAt(h2) + b64.charAt(h3) + b64.charAt(h4);
  }
  coded = e.join(''); // join() is far faster than repeated string concatenation in IE
  // replace 'A's from padded nulls with '='s
  coded = coded.slice(0, coded.length - pad.length) + pad;

  return coded;
};

/**
 * Decode string from Base64, as defined by RFC 4648 [http://tools.ietf.org/html/rfc4648]
 * (instance method extending String object). As per RFC 4648, newlines are not catered for.
 *
 * @param {String} str The string to be decoded from base-64
 * @param {Boolean} [utf8decode=false] Flag to indicate whether str is Unicode string to be decoded 
 *   from UTF8 after conversion from base64
 * @returns {String} decoded string
 */
Base64.decode = function (str, utf8decode) {
  utf8decode = (typeof utf8decode == 'undefined') ? false : utf8decode;
  var o1, o2, o3, h1, h2, h3, h4, bits, d = [],
    plain, coded;
  var b64 = Base64.code;

  coded = utf8decode ? str.decodeUTF8() : str;

  for (var c = 0; c < coded.length; c += 4) { // unpack four hexets into three octets
    h1 = b64.indexOf(coded.charAt(c));
    h2 = b64.indexOf(coded.charAt(c + 1));
    h3 = b64.indexOf(coded.charAt(c + 2));
    h4 = b64.indexOf(coded.charAt(c + 3));

    bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;

    o1 = bits >>> 16 & 0xff;
    o2 = bits >>> 8 & 0xff;
    o3 = bits & 0xff;

    d[c / 4] = String.fromCharCode(o1, o2, o3);
    // check for padding
    if (h4 == 0x40) d[c / 4] = String.fromCharCode(o1, o2);
    if (h3 == 0x40) d[c / 4] = String.fromCharCode(o1);
  }
  plain = d.join(''); // join() is far faster than repeated string concatenation in IE
  return utf8decode ? plain.decodeUTF8() : plain;
};

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  Utf8 class: encode / decode between multi-byte Unicode characters and UTF-8 multiple          */
/*              single-byte character encoding (c) Chris Veness 2002-2011                         */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

var Utf8 = {}; // Utf8 namespace

/**
 * Encode multi-byte Unicode string into utf-8 multiple single-byte characters 
 * (BMP / basic multilingual plane only)
 *
 * Chars in range U+0080 - U+07FF are encoded in 2 chars, U+0800 - U+FFFF in 3 chars
 *
 * @param {String} strUni Unicode string to be encoded as UTF-8
 * @returns {String} encoded string
 */
Utf8.encode = function (strUni) {
  // use regular expressions & String.replace callback function for better efficiency 
  // than procedural approaches
  var strUtf = strUni.replace(/[\u0080-\u07ff]/g, // U+0080 - U+07FF => 2 bytes 110yyyyy, 10zzzzzz

  function (c) {
    var cc = c.charCodeAt(0);
    return String.fromCharCode(0xc0 | cc >> 6, 0x80 | cc & 0x3f);
  });
  strUtf = strUtf.replace(/[\u0800-\uffff]/g, // U+0800 - U+FFFF => 3 bytes 1110xxxx, 10yyyyyy, 10zzzzzz

  function (c) {
    var cc = c.charCodeAt(0);
    return String.fromCharCode(0xe0 | cc >> 12, 0x80 | cc >> 6 & 0x3F, 0x80 | cc & 0x3f);
  });

  return strUtf;
};

/**
 * Decode utf-8 encoded string back into multi-byte Unicode characters
 *
 * @param {String} strUtf UTF-8 string to be decoded back to Unicode
 * @returns {String} decoded string
 */
Utf8.decode = function (strUtf) {
  // note: decode 3-byte chars first as decoded 2-byte strings could appear to be 3-byte char!
  var strUni = strUtf.replace(/[\u00e0-\u00ef][\u0080-\u00bf][\u0080-\u00bf]/g, // 3-byte chars

  function (c) { // (note parentheses for precence)
    var cc = ((c.charCodeAt(0) & 0x0f) << 12) | ((c.charCodeAt(1) & 0x3f) << 6) | (c.charCodeAt(2) & 0x3f);
    return String.fromCharCode(cc);
  });

  strUni = strUni.replace(/[\u00c0-\u00df][\u0080-\u00bf]/g, // 2-byte chars

  function (c) { // (note parentheses for precence)
    var cc = (c.charCodeAt(0) & 0x1f) << 6 | c.charCodeAt(1) & 0x3f;
    return String.fromCharCode(cc);
  });

  return strUni;
};

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

// Usage: this implementation would be invoked as follows:
var password = 'L0ck it up saf3';
var plaintext = 'pssst ... Ä‘on't tell anyøne!';

var ciphertext = Aes.Ctr.encrypt(plaintext, password, 256);
var origtext = Aes.Ctr.decrypt(ciphertext, password, 256);