CODEWITHSUNDEEP
phparraysxor
Ega Suhandianto
Ega Suhandianto

Reputation: 27

why is xor binary out numbered

I have a problem, why the result of xor p [i] with k is 00000238. It should be 00000110.

<?php
$Ciphertext = array();
$C = array();
$iv = 0;
$Kunci = "U";
$spsi= " ";
$Plaintext =$spsi."S";

$c0 = sprintf("%08d", 
decbin($iv));
$key =  dechex(ord($Kunci))  $k=sprintf("%08d",decbin(hexdec($key)));

$C[0]=$c0;
$P = array();
for($i =1;$i<strlen($Plaintext); $i++){
$P[$i] = dechex(ord($Plaintext[$i]));
$P[$i] = sprintf("%08d",decbin(hexdec($P[$i])));

$C[$i]=sprintf("%08d",(intval($P[$i])^intval($C[$i-1])));
$C[$i]=sprintf("%08d",(intval($C[$i])^intval($k)));

//$C[$i] = (bindec($C[$i]))<<1;
//if ($C[$i]>255)$C[$i]-=255;
//$C[$i] = sprintf("%08d", decbin($C[$i]));
//$Ciphertext[$i] = strtoupper(str_pad(dechex(bindec($C[$i])),2,"0",STR_PAD_LEFT));


}               
echo "<br/>";
print_r($P);
echo "<br/>";
print_r($C);
echo "<br/>";
print_r($Ciphertext);
//echo implode(",", $P);
?>

And output :

Array ( [1] => 01010011 ) Array ( [0] => 00000000 [1] => 00000238 ) Array ( )

I want to make a program like in the picture link. https://i.sstatic.net/mcBol.png

I want to fetch these values in this manner:

P1: 01010011
C0: 00000000

C1: XOR of P1 and C0

C1: 01010101
K:  01010101

C1: XOR of C1 and K

P2: 01100000
C1: 00001100

C2: XOR of P2 and C1

C2: 01111110
K:  01010101

C2: XOR of C2 and K

etc...

Upvotes: 1

Views: 79

Answers (1)

bestprogrammerintheworld
bestprogrammerintheworld

Reputation: 5520

<?php
$p = array(
    '01010011',
    '01110000',
    '01100001',
    '01110010'
);
$controlbits = get_controlbits($p);


function get_controlbits(array $p) {
    $k = '01010101';
    $c = array('00000000');

    $c_key = 1;

    foreach($p as $p_item) {
        $prev_c = $c[$c_key-1];    

        //XOR of $p_item and  previous $c[$c_key-1] 
        $c[$c_key] = _xor($prev_c, $p_item); 

        //XOR of current $c with $k
        $c[$c_key] = _xor($c[$c_key], $k);

        //Shift left bit   
        $c[$c_key] = bitshift_left($c[$c_key]);

        $c_key++;
    }

    return $c;
}

function bitshift_left($text){
    $text = substr($text, 1,7) . '0';
    return $text;
}

//From https://stackoverflow.com/questions/14365032/xor-binary-in-php
function _xor($text,$key){
    for($i=0; $i<strlen($text); $i++){
        $text[$i] = intval($text[$i])^intval($key[$i]);
    }
    return $text;
}

output with code:

echo '<pre>';
print_r($controlbits);
echo '</pre>';

output result:

Array
(
    [0] => 00000000
    [1] => 00001100
    [2] => 01010010
    [3] => 11001100
    [4] => 11010110
)

Upvotes: 1

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