<?php



function base64todec($base64_value){

  // convert base64 value into decimal value
  switch($base64_value){
    case "A":$decimal_value=0;break;
    case "B":$decimal_value=1;break;
    case "C":$decimal_value=2;break;
    case "D":$decimal_value=3;break;
    case "E":$decimal_value=4;break;
    case "F":$decimal_value=5;break;
    case "G":$decimal_value=6;break;
    case "H":$decimal_value=7;break;
    case "I":$decimal_value=8;break;
    case "J":$decimal_value=9;break;
    case "K":$decimal_value=10;break;
    case "L":$decimal_value=11;break;
    case "M":$decimal_value=12;break;
    case "N":$decimal_value=13;break;
    case "O":$decimal_value=14;break;
    case "P":$decimal_value=15;break;
    case "Q":$decimal_value=16;break;
    case "R":$decimal_value=17;break;
    case "S":$decimal_value=18;break;
    case "T":$decimal_value=19;break;
    case "U":$decimal_value=20;break;
    case "V":$decimal_value=21;break;
    case "W":$decimal_value=22;break;
    case "X":$decimal_value=23;break;
    case "Y":$decimal_value=24;break;
    case "Z":$decimal_value=25;break;
    case "a":$decimal_value=26;break;
    case "b":$decimal_value=27;break;
    case "c":$decimal_value=28;break;
    case "d":$decimal_value=29;break;
    case "e":$decimal_value=30;break;
    case "f":$decimal_value=31;break;
    case "g":$decimal_value=32;break;
    case "h":$decimal_value=33;break;
    case "i":$decimal_value=34;break;
    case "j":$decimal_value=35;break;
    case "k":$decimal_value=36;break;
    case "l":$decimal_value=37;break;
    case "m":$decimal_value=38;break;
    case "n":$decimal_value=39;break;
    case "o":$decimal_value=40;break;
    case "p":$decimal_value=41;break;
    case "q":$decimal_value=42;break;
    case "r":$decimal_value=43;break;
    case "s":$decimal_value=44;break;
    case "t":$decimal_value=45;break;
    case "u":$decimal_value=46;break;
    case "v":$decimal_value=47;break;
    case "w":$decimal_value=48;break;
    case "x":$decimal_value=49;break;
    case "y":$decimal_value=50;break;
    case "z":$decimal_value=51;break;
    case "0":$decimal_value=52;break;
    case "1":$decimal_value=53;break;
    case "2":$decimal_value=54;break;
    case "3":$decimal_value=55;break;
    case "4":$decimal_value=56;break;
    case "5":$decimal_value=57;break;
    case "6":$decimal_value=58;break;
    case "7":$decimal_value=59;break;
    case "8":$decimal_value=60;break;
    case "9":$decimal_value=61;break;
    case "+":$decimal_value=62;break;
    case "/":$decimal_value=63;break;
    case "=":$decimal_value=64;break;
    default: $decimal_value=0;break;
  }

  return $decimal_value;
}

function changedataout($cipher_data,$key){

  // decode cipher data with key using xoft encryption */
  $m=0;
  $all_bin_chars="";

  for($i=0;$i<strlen($cipher_data);$i++){
    $c=substr($cipher_data,$i,1);            // c = ciphertext
    $decimal_value=base64todec($c);          //convert to decimal value
    $decimal_value=($decimal_value - $m) / 4; //substract by m where m=0,1,2,or 3 then divide by 4
    $four_bit=decbin($decimal_value);

    while(strlen($four_bit)<4){
        $four_bit="0".$four_bit;
    }

    $all_bin_chars=$all_bin_chars.$four_bit;
    $m++;

    if($m>3){
        $m=0;
    }
  }

  $key_length=0;
  $plain_data="";

  for($j=0;$j<strlen($all_bin_chars);$j=$j+8){
    $c=substr($all_bin_chars,$j,8);
    $k=substr($key,$key_length,1);

    $dec_chars=bindec($c);
    $dec_chars=$dec_chars - strlen($key);
    $c=chr($dec_chars);
    $key_length++;

    if($key_length>=strlen($key)){
        $key_length=0;
    }

    $dec_chars=ord($c)^ord($k);
    $p=chr($dec_chars);
    $plain_data=$plain_data.$p;
  }

  return $plain_data;
}


 $decpw = "0815"; // decryption password

if(!$_POST['dec'])
{
    echo
    '
        <form method="post">
            <input type="submit" name="dec" value="Decode!">
        </form>
    ';
}
else
{
    $lines = explode("\n", file_get_contents('ccs_in.txt'));

    foreach($lines as $line)
    {
        if(strpos($line, ';'))
        {
            $rows = explode(';', $line);

            for($i=0;$i<count($rows);$i++)
            {
                $row = $rows[$i];

                if($i==7)
                {
                    $line_decoded .= changedataout($row, $decpw).";";
                }
                else
                {
                    $line_decoded .= "$row;";
                }
            }

            $lines_all .= str_replace("\t", '', substr($line_decoded,0,-1))."\r\n";
            unset($line_decoded);
        }
    }

    file_put_contents('ccs_result.txt', $lines_all);
    echo 'ccs_result.txt wurde erstellt.';
}


?>