  | $key = "This is supposed to be a secret key !!!"; 
  function keyED($txt,$encrypt_key)  {  $encrypt_key = md5($encrypt_key);  $ctr=0;  $tmp = "";  for ($i=0;$i {  if ($ctr==strlen($encrypt_key)) $ctr=0;  $tmp.= substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1);  $ctr++;  }  return $tmp;  } 
  function encrypt($txt,$key)  {  srand((double)microtime()*1000000);  $encrypt_key = md5(rand(0,32000));  $ctr=0;  $tmp = "";  for ($i=0;$i {  if ($ctr==strlen($encrypt_key)) $ctr=0;  $tmp.= substr($encrypt_key,$ctr,1) .  (substr($txt,$i,1) ^ substr($encrypt_key,$ctr,1));  $ctr++;  }  return keyED($tmp,$key);  } 
  function decrypt($txt,$key)  {  $txt = keyED($txt,$key);  $tmp = "";  for ($i=0;$i {  $md5 = substr($txt,$i,1);  $i++;  $tmp.= (substr($txt,$i,1) ^ $md5);  }  return $tmp;  } 
  $string = "Hello World !!!"; 
  // encrypt $string, and store it in $enc_text  $enc_text = encrypt($string,$key); 
  // decrypt the encrypted text $enc_text, and store it in $dec_text  $dec_text = decrypt($enc_text,$key); 
  print "Original text : $string  \n";  print "Encrypted text : $enc_text  \n";  print "Decrypted text : $dec_text  \n";  ?> 
 
  
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