Lập trình PHP - Mã hóa file bằng md5

Tạo và mã hóa file với phép xor theo bytes và một khóa.
Phương pháp mã hóa tốt nhưng tốc độ giảm 2 lần, chỉ 520KB/s.
Sử dụng hàm băm md5 password.
Mã
<?php
// Stream files and encrypt the data on-the-fly

// Settings
// -- File to stream
$file = "FILE_out";
// -- Reading buffer
$bufferlength = 3840;
// -- Key in hex
//$keychar = "9cdfb439c7876e703e307864c9167a15";

// Function: Convertion hex key in a string into binary
function hex2bin($h) {
if (!is_string($h)) return null;
$r = array();
for ($a=0; ($a*2)<strlen($h); $a++) {
$ta = hexdec($h[2*$a]);
$tb = hexdec($h[(2*$a+1)]);
$r[$a] = (int) (($ta << 4) + $tb);
}
return $r;
}

// Function to send the auth headers
function askPassword($text="Enter the password") {
header('WWW-Authenticate: Basic realm="'. utf8_decode($text) .'"');
header('HTTP/1.0 401 Unauthorized');
return 1;
}

// Key is asked at the first start
if (!isset($_SERVER['PHP_AUTH_PW'])) {
askPassword();
echo "Une clé est nécessaire ! ";
exit;
}
// Get the key in hex
$keychar = $_SERVER['PHP_AUTH_PW'];

// Convert key and set the size of the key
$key = hex2bin($keychar);
$keylength = count($key);
// Teste si la clé est valide en hex
if ($key == "" || $keylength <= 4) {
askPassword("Clé incorrecte !");
//echo "Clé incorrecte ! ";
exit();
}
// Teste si la clé est de longueur d'une puissance de 2
if ( ($keylength%2) != 0) {
askPassword("Clé de longueur incorrecte (multiple de 2 uniquement)");
//echo "Clé de longueur incorrecte (puissance de 2 uniquement) ";
exit();
}

// Headers
header("Content-Type: application/octet-stream; ");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . filesize($file) ."; ");
header("filename=\"".$file."\"; ");
flush(); // this doesn't really matter.

// Opening the file in read-only
$fp = fopen($file, "r");
while (!feof($fp))
{
// Read a buffer size of the file
$buffer = fread($fp, $bufferlength);
$j=0;
for ($i=0; $i < $bufferlength; $i++) {
// The key is read in loop to crypt the whole file
if ($i%$keylength == 0) {
$j=0;
}
// Apply a xor operation between the key and the file to crypt
// This operation eats a lots of CPU time (Stream at 1MiB/s on my server; Intel E2180)
$tmp = pack("C", $key[$j]);
$bufferE = ( $buffer[$i]^$tmp); // <==== Le fameux XOR

/*
echo " key[".$j."]: ";
var_dump($tmp);
echo " buffer[".$i."]: ";
var_dump($buffer[$i]);
echo " bufferE: ";
var_dump($bufferE);
echo " ";
//*/

// Send the encrypted data
echo $bufferE;
// Clean the memory
$bufferE = "";
$j++;
}
$buffer = "";
flush(); // this is essential for large downloads
/*
fclose($fp);
exit();
//*/
}
// Close the file and it's finished
fclose($fp);

?>
Nguồn php.net