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AES Shortcut

By Gianni Amato Last update Jun 24, 2009 — Installed 85 times. Daily Installs: 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0

There are 1 previous version of this script.

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// ==UserScript==
// @name	AES Shortcut
// @author  	Gianni 'guelfoweb' Amato http://www.guelfoweb.com
// @description AES 256 Text Encrypt/Decrypt
// @include	*
// @version     0.0.1
// @date        2009-06-24

// ==/UserScript==

// Encrypt: select plain text and press Ctrl+Shift+E
// Decrypt: select cipher text and press Ctrl+Shift+D

shortcut("Ctrl+Shift+E",function() { getSelectedText('E'); }); // Encrypt
shortcut("Ctrl+Shift+D",function() { getSelectedText('D'); }); // Decrypt

function getSelectedText(action) {
    var txt = '';
     if (window.getSelection)  {
        txt = window.getSelection();
     }
     else if (document.getSelection)  {
        txt = document.getSelection();
     }
     else if (document.selection)  {
        txt = document.selection.createRange().text;
     }
    
    if (txt == '')  {
     	return false; // field empty
    }
    
    var pass = prompt('Please enter password', '');
    if(pass){
	var txtplain = String(txt);
	var passplain = String(pass);
	    if (action == "E"){
	    	prompt('Encrypted text', AESEncryptCtr(txtplain, passplain, 256)); // Encrypt
	    	return false;
	    }
	    if (action == "D"){
	    	prompt('Decrypted text', AESDecryptCtr(txtplain, passplain, 256)); // Decrypt
	    	return false;
	    }
    }
    else return;
};


function shortcut(shortcut,callback,opt) {
	//Provide a set of default options
	var default_options = {
		'type':'keydown',
		'propagate':false,
		'target':document
	}
	if(!opt) opt = default_options;
	else {
		for(var dfo in default_options) {
			if(typeof opt[dfo] == 'undefined') opt[dfo] = default_options[dfo];
		}
	}

	var ele = opt.target
	if(typeof opt.target == 'string') ele = document.getElementById(opt.target);
	var ths = this;

	//The function to be called at keypress
	var func = function(e) {
		e = e || window.event;
		
		//Find Which key is pressed
		if (e.keyCode) code = e.keyCode;
		else if (e.which) code = e.which;
		var character = String.fromCharCode(code).toLowerCase();

		var keys = shortcut.toLowerCase().split("+");
		//Key Pressed - counts the number of valid keypresses - if it is same as the number of keys, the shortcut function is invoked
		var kp = 0;
		
		//Work around for stupid Shift key bug created by using lowercase - as a result the shift+num combination was broken
		var shift_nums = {
			"`":"~",
			"1":"!",
			"2":"@",
			"3":"#",
			"4":"$",
			"5":"%",
			"6":"^",
			"7":"&",
			"8":"*",
			"9":"(",
			"0":")",
			"-":"_",
			"=":"+",
			";":":",
			"'":"\"",
			",":"<",
			".":">",
			"/":"?",
			"\\":"|"
		}
		//Special Keys - and their codes
		var special_keys = {
			'esc':27,
			'escape':27,
			'tab':9,
			'space':32,
			'return':13,
			'enter':13,
			'backspace':8,

			'scrolllock':145,
			'scroll_lock':145,
			'scroll':145,
			'capslock':20,
			'caps_lock':20,
			'caps':20,
			'numlock':144,
			'num_lock':144,
			'num':144,
			
			'pause':19,
			'break':19,
			
			'insert':45,
			'home':36,
			'delete':46,
			'end':35,
			
			'pageup':33,
			'page_up':33,
			'pu':33,

			'pagedown':34,
			'page_down':34,
			'pd':34,

			'left':37,
			'up':38,
			'right':39,
			'down':40,

			'f1':112,
			'f2':113,
			'f3':114,
			'f4':115,
			'f5':116,
			'f6':117,
			'f7':118,
			'f8':119,
			'f9':120,
			'f10':121,
			'f11':122,
			'f12':123
		}


		for(var i=0; k=keys[i],i<keys.length; i++) {
			//Modifiers
			if(k == 'ctrl' || k == 'control') {
				if(e.ctrlKey) kp++;

			} else if(k ==  'shift') {
				if(e.shiftKey) kp++;

			} else if(k == 'alt') {
					if(e.altKey) kp++;

			} else if(k.length > 1) { //If it is a special key
				if(special_keys[k] == code) kp++;

			} else { //The special keys did not match
				if(character == k) kp++;
				else {
					if(shift_nums[character] && e.shiftKey) { //Stupid Shift key bug created by using lowercase
						character = shift_nums[character]; 
						if(character == k) kp++;
					}
				}
			}
		}

		if(kp == keys.length) {
			callback(e);

			if(!opt['propagate']) { //Stop the event
				//e.cancelBubble is supported by IE - this will kill the bubbling process.
				e.cancelBubble = true;
				e.returnValue = false;

				//e.stopPropagation works only in Firefox.
				if (e.stopPropagation) {
					e.stopPropagation();
					e.preventDefault();
				}
				return false;
			}
		}
	}

	//Attach the function with the event	
	if(ele.addEventListener) ele.addEventListener(opt['type'], func, false);
	else if(ele.attachEvent) ele.attachEvent('on'+opt['type'], func);
	else ele['on'+opt['type']] = func;
}





/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  AES implementation in JavaScript (c) Chris Veness 2005-2008                                   */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/*
 * AES Cipher function: encrypt 'input' with Rijndael algorithm
 *
 *   takes   byte-array 'input' (16 bytes)
 *           2D byte-array key schedule 'w' (Nr+1 x Nb bytes)
 *
 *   applies Nr rounds (10/12/14) using key schedule w for 'add round key' stage
 *
 *   returns byte-array encrypted value (16 bytes)
 */
function Cipher(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 = AddRoundKey(state, w, 0, Nb);

  for (var round=1; round<Nr; round++) {
    state = SubBytes(state, Nb);
    state = ShiftRows(state, Nb);
    state = MixColumns(state, Nb);
    state = AddRoundKey(state, w, round, Nb);
  }

  state = SubBytes(state, Nb);
  state = ShiftRows(state, Nb);
  state = 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;
}


function SubBytes(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] = Sbox[s[r][c]];
  }
  return s;
}


function ShiftRows(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 fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf 
}


function MixColumns(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;
}


function AddRoundKey(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;
}

function KeyExpansion(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 = SubWord(RotWord(temp));
      for (var t=0; t<4; t++) temp[t] ^= Rcon[i/Nk][t];
    } else if (Nk > 6 && i%Nk == 4) {
      temp = SubWord(temp);
    }
    for (var t=0; t<4; t++) w[i][t] = w[i-Nk][t] ^ temp[t];
  }

  return w;
}

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

function RotWord(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]
var 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]
var 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] ]; 


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

/** 
 * Encrypt a text using AES encryption in Counter mode of operation
 *  - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
 *
 * Unicode multi-byte character safe
 *
 * @param plaintext source text to be encrypted
 * @param password  the password to use to generate a key
 * @param nBits     number of bits to be used in the key (128, 192, or 256)
 * @return          encrypted text
 */
function AESEncryptCtr(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 = plaintext.encodeUTF8();
  password = password.encodeUTF8();
  //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 = Cipher(pwBytes, KeyExpansion(pwBytes));  // gives us 16-byte key
  key = key.concat(key.slice(0, nBytes-16));  // expand key to 16/24/32 bytes long

  // initialise counter block (NIST SP800-38A §B.2): millisecond time-stamp for nonce in 1st 8 bytes,
  // block counter in 2nd 8 bytes
  var counterBlock = new Array(blockSize);
  var nonce = (new Date()).getTime();  // timestamp: milliseconds since 1-Jan-1970
  var nonceSec = Math.floor(nonce/1000);
  var nonceMs = nonce%1000;
  // encode nonce with seconds in 1st 4 bytes, and (repeated) ms part filling 2nd 4 bytes
  for (var i=0; i<4; i++) counterBlock[i] = (nonceSec >>> i*8) & 0xff;
  for (var i=0; i<4; i++) counterBlock[i+4] = nonceMs & 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 = 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 = 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
  var ciphertext = ctrTxt + ciphertxt.join('');
  ciphertext = ciphertext.encodeBase64();  // encode in base64
  
  //alert((new Date()) - t);
  return ciphertext;
}

/** 
 * Decrypt a text encrypted by AES in counter mode of operation
 *
 * @param ciphertext source text to be encrypted
 * @param password   the password to use to generate a key
 * @param nBits      number of bits to be used in the key (128, 192, or 256)
 * @return           decrypted text
 */
function AESDecryptCtr(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 = ciphertext.decodeBase64();
  password = password.encodeUTF8();
  //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 = Cipher(pwBytes, 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 = 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 = 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 = plaintext.decodeUTF8();  // decode from UTF8 back to Unicode multi-byte chars
  
  //alert((new Date()) - t);
  return plaintext;
}

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

/**
 * 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 utf8encode optional parameter, if set to true Unicode string is encoded to UTF8 before 
 *                   conversion to base64; otherwise string is assumed to be 8-bit characters
 * @return           base64-encoded string
 */ 
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

String.prototype.encodeBase64 = function(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;
   
  plain = utf8encode ? this.encodeUTF8() : this;
  
  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 b64 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
  
  // 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 utf8decode optional parameter, if set to true UTF8 string is decoded back to Unicode  
 *                   after conversion from base64
 * @return           decoded string
 */ 
String.prototype.decodeBase64 = function(utf8decode) {
  utf8decode =  (typeof utf8decode == 'undefined') ? false : utf8decode;
  var o1, o2, o3, h1, h2, h3, h4, bits, d=[], plain, coded;

  coded = utf8decode ? this.decodeUTF8() : this;
  
  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
   
  return utf8decode ? plain.decodeUTF8() : plain; 
}

/**
 * Encode multi-byte Unicode string into utf-8 multiple single-byte characters 
 * (BMP / basic multilingual plane only) (instance method extending String object).
 *
 * Chars in range U+0080 - U+07FF are encoded in 2 chars, U+0800 - U+FFFF in 3 chars
 *
 * @return encoded string
 */
String.prototype.encodeUTF8 = function() {
  // use regular expressions & String.replace callback function for better efficiency 
  // than procedural approaches
  var str = this.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); }
    );
  str = str.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 str;
}

/**
 * Decode utf-8 encoded string back into multi-byte Unicode characters
 * (instance method extending String object).
 *
 * @return decoded string
 */
String.prototype.decodeUTF8 = function() {
  var str = this.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); }
    );
  str = str.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); }
    );
  return str;
}

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

function byteArrayToHexStr(b) {  // convert byte array to hex string for displaying test vectors
  var s = '';
  for (var i=0; i<b.length; i++) s += b[i]<0x10 ? '0'+b[i].toString(16)+' ' : b[i].toString(16)+' ';
  return s;
}

String.prototype.toCodes = function() {
  if (this.length == 0) return '';
  var arr = this.split('');
  for (a in arr) arr[a] = arr[a].charCodeAt(0);
  return arr.join(':');
}

function verifyKeyExpansion() {
  var cipher = [0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 
                0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c];
  alert('128: '+keyScheduleToHexStr(KeyExpansion(cipher)));
  var cipher = [0x8e, 0x73, 0xb0, 0xf7, 0xda, 0x0e, 0x64, 0x52, 
                0xc8, 0x10, 0xf3, 0x2b, 0x80, 0x90, 0x79, 0xe5, 
                0x62, 0xf8, 0xea, 0xd2, 0x52, 0x2c, 0x6b, 0x7b];
  alert('192: '+keyScheduleToHexStr(KeyExpansion(cipher)));
  var cipher = [0x60, 0x3d, 0xeb, 0x10, 0x15, 0xca, 0x71, 0xbe, 
                0x2b, 0x73, 0xae, 0xf0, 0x85, 0x7d, 0x77, 0x81, 
                0x1f, 0x35, 0x2c, 0x07, 0x3b, 0x61, 0x08, 0xd7, 
                0x2d, 0x98, 0x10, 0xa3, 0x09, 0x14, 0xdf, 0xf4];
  alert('256: '+keyScheduleToHexStr(KeyExpansion(cipher)));
}

function keyScheduleToHexStr(keySchedule) {  // return expanded key as hex words, as per FIPS-197§A
  var d = '';
  for (w=0; w<keySchedule.length; w++) {
    for (var b=0; b<4; b++) {
      var byte = keySchedule[w][b];
      d += byte<0x10 ? '0'+byte.toString(16) : byte.toString(16);
    }
    d += ' ';
  }
  return d;
}

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