Often we find the need to protect certain files so that if they are ever subject to unauthorized accessed, the contents can be safe. Encrypting info in a database is pretty straightforward, however encrypting files in a directory is not always. Here are two functions to encrypt and decrypt whole files using PHP and Mcrypt.
function encrypt_file($source,$destination,$passphrase,$stream=NULL) {
// $source can be a local file...
if($stream) {
$contents = $source;
// OR $source can be a stream if the third argument ($stream flag) exists.
}else{
$handle = fopen($source, "rb");
$contents = fread($handle, filesize($source));
fclose($handle);
}
$iv = substr(md5("\x1B\x3C\x58".$passphrase, true), 0, 8);
$key = substr(md5("\x2D\xFC\xD8".$passphrase, true) . md5("\x2D\xFC\xD9".$passphrase, true), 0, 24);
$opts = array('iv'=>$iv, 'key'=>$key);
$fp = fopen($destination, 'wb') or die("Could not open file for writing.");
stream_filter_append($fp, 'mcrypt.tripledes', STREAM_FILTER_WRITE, $opts);
fwrite($fp, $contents) or die("Could not write to file.");
fclose($fp);
}
Below is the function to perform decryption.
function decrypt_file($file,$passphrase) {
$iv = substr(md5("\x1B\x3C\x58".$passphrase, true), 0, 8);
$key = substr(md5("\x2D\xFC\xD8".$passphrase, true) .
md5("\x2D\xFC\xD9".$passphrase, true), 0, 24);
$opts = array('iv'=>$iv, 'key'=>$key);
$fp = fopen($file, 'rb');
stream_filter_append($fp, 'mdecrypt.tripledes', STREAM_FILTER_READ, $opts);
return $fp;
}
Encryption Example:
encrypt_file('/path/to/source/file', '/path/to/destination/file', 'MySuperSecretPassword');
Decryption Example:
// Output to inline PDF
$decrypted = decrypt_file('/path/to/file','MySuperSecretPassword');
header('Content-type: application/pdf');
fpassthru($decrypted);
// Output to a string for email attachments, etc.
$decrypted = decrypt_file('/path/to/file','MySuperSecretPassword');
$contents = stream_get_contents($fp);
(Just to make sure, you need to change $passphrase into your very own password and keep it secret.)
Source: Monkey Logic
