text: (function(){
  
  // Shortcut
  var util = Crypto.util;
  
  Crypto.PBKDF2 = function (password, salt, keylen, options) {
  
  	// Defaults
  	var hasher = options && options.hasher || Crypto.SHA1,
  	    iterations = options && options.iterations || 1;
  
  	// Pseudo-random function
  	function PRF(password, salt) {
  		return Crypto.HMAC(hasher, salt, password, { asBytes: true });
  	}
  
  	// Generate key
  	var derivedKeyBytes = [],
  	    blockindex = 1;
  	while (derivedKeyBytes.length < keylen) {
  
  		var block = PRF(password, salt + util.bytesToString(
  		                                 util.wordsToBytes([blockindex])));
  
  		for (var u = block, i = 1; i < iterations; i++) {
  			u = PRF(password, util.bytesToString(u));
  			for (var j = 0; j < block.length; j++) block[j] ^= u[j];
  		}
  
  		derivedKeyBytes = derivedKeyBytes.concat(block);
  		blockindex++;
  
  	}
  
  	// Truncate excess bytes
  	derivedKeyBytes.length = keylen;
  
  	return options && options.asBytes ? derivedKeyBytes :
  	       options && options.asString ? util.bytesToString(derivedKeyBytes) :
  	       util.bytesToHex(derivedKeyBytes);
  
  };
  
  })();
  