Re: strings to number and XOR

in reply to strings to number and XOR

$msg = "this is a test messagez";
$key = "\x4f\xcb";   # or  $key = pack "n", 0x4fcb;

$xored = $msg ^ $key;

print join("  ", split(//, $msg)), "\n";
print join(" ", unpack("(H2)*", $msg)),   "\n";
print join(" ", unpack("(H2)*", $key)),   "\n";
print join(" ", unpack("(H2)*", $xored)), "\n";

__END__
t  h  i  s     i  s     a     t  e  s  t     m  e  s  s  a  g  e  z
74 68 69 73 20 69 73 20 61 20 74 65 73 74 20 6d 65 73 73 61 67 65 7a
4f cb
3b a3 69 73 20 69 73 20 61 20 74 65 73 74 20 6d 65 73 73 61 67 65 7a
[download]

The easiest way to generate your key string for the entire message is probably something like

    $key = "\x4f\xcb" x (length($msg)/2);
or
    $key = pack("n", 0x4fcb) x (length($msg)/2);
[download]

That way you can directly XOR both strings without any further ado:

t  h  i  s     i  s     a     t  e  s  t     m  e  s  s  a  g  e  z
74 68 69 73 20 69 73 20 61 20 74 65 73 74 20 6d 65 73 73 61 67 65 7a  
+ $msg
4f cb 4f cb 4f cb 4f cb 4f cb 4f cb 4f cb 4f cb 4f cb 4f cb 4f cb     
+ $key
3b a3 26 b8 6f a2 3c eb 2e eb 3b ae 3c bf 6f a6 2a b8 3c aa 28 ae 7a  
+ XOR result
[download]

___

$xitem = unpack("H*", $array[1]) ^ $key;

What this is doing is XORing the hex-string "7468" (i.e. 4 ASCII chars, hex 37 34 36 38) with the Perl internal representation of the number 0x4fcb ...

In Section Seekers of Perl Wisdom