mcrypt_generic

(PHP 4 >= 4.0.2, PHP 5)

mcrypt_genericEsta función encripta datos

Descripción

string mcrypt_generic ( resource $td , string $data )

Esta función encripta datos. Estos datos son rellenados con "\0" para asegurarse de que la longitud de los datos sea n * blocksize. Esta función devuelve los datos cifrados. Note que la longitud de la cadena devuelta puede ser más larga que la de entrada, debido al relleno de la información.

Si se desea almacenar los datos en una base de datos se debe asegurar que la cadena completa retornada por mcrypt_generic se almacene, o la cadena no será desencriptada apropiadamente. Si la cadena original tiene una longitud de 10 caracteres, y el tamaño del bloque es 8 (utilice mcrypt_enc_get_block_size() para determinar el tamaño del bloque), serán necerarios al menos 16 caracteres en el campo de su base de datos. Tenga en cuenta que la cadena devuelta por mdecrypt_generic() será también de 16 caracteres. Utilice rtrim($str, "\0") para remover el relleno.

Si se está, por ejemplo, almacenando los datos en una base de datos MySQL, se debe tener en cuenta que durante la inserción en campos varchar, los espacios finales son removidos. Ya que la información cifrada puede finalizar con un espacio (ASCII 32), los datos serán dañados por esta remoción. En cambio, almacene los datos en un campo tinyblob/tinytext (o mayor).

Parámetros

td

El descriptor de cifrado.

El gestor de cifrado debería siempre ser inicializado con mcrypt_generic_init() con una clave y un IV antes de invocar a esta función. Cuando el cifrado haya terminado, se debería liberar los buffers de cifrado al invocar a mcrypt_generic_deinit() Véase mcrypt_module_open() para un ejemplo.

data

Los datos a encriptar.

Valores devueltos

Devuelve la información cifrada.

Ver también

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User Contributed Notes 7 notes

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5
tmacedo at linux dot ime dot usp dot br
7 years ago
completing  the post from Ryan Thomas, ryanrst at gmail dot com, if u post a cookie w/ HTTP method, its may be encoded;
As some chars in base64 will be encoded to another things, u can just replace them before encode and after decode;
Its a tweak from dawgeatschikin at hotmail dot com to original idea from massimo dot scamarcia at gmail dot com
(see @ http://www.php.net/manual/en/function.base64-encode.php):
<?php
function urlsafe_b64encode($string)
{
 
$data = base64_encode($string);
 
$data = str_replace(array('+','/','='),array('-','_','.'),$data);
  return
$data;
}
function
urlsafe_b64decode($string)
{
 
$data = str_replace(array('-','_','.'),array('+','/','='),$string);
 
$mod4 = strlen($data) % 4;
  if (
$mod4) {
   
$data .= substr('====', $mod4);
  }
  return
base64_decode($data);
}
?>
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1
maxximus007 at gmail dot com
7 years ago
Behaviour change: Since 5.2.x mcrypt_generic will issue a warning when the datastring is empty.
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1
chad 0x40 herballure 0x2e com
8 years ago
Addendum to my previous note: apparently there was some sort of character encoding breakage; PHP does not pad if no padding is needed, and the extra padding I saw was the result of chr(X) returning multiple bytes or something.

The pad/unpad functions I gave are still binary-safe, though, and are to the best of my knowledge completely compatible with NIST 800-38a.
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1
chad 0x40 herballure 0x2e com
8 years ago
If the data is already n*blocksize long, PHP pads with another full block of "\0", so there will be between 1 and mcrypt_enc_get_block_size($td) bytes of padding.

You can create binary-safe padding by unconditionally adding a 0x80 to the string, then stripping trailing "\0"s PHP added, plus the one 0x80 byte.

<?php
function pad($text) {
 
// Add a single 0x80 byte and let PHP pad with 0x00 bytes.
 
return pack("a*H2", $text, "80");
}
function
unpad($text) {
 
// Return all but the trailing 0x80 from text that had the 0x00 bytes removed
 
return substr(rtrim($text, "\0"), 0, -1);
}
?>
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1
Ryan Thomas, ryanrst at gmail dot com
8 years ago
If you wish to store encrypted data in a cookie variable on the browser you will encounter problems when decrypting the data. This is because cookies will only store US-ASCII characters and your encrypted data may contain non-US-ASCII characters.

The solution:

base64_encode your encrypted string before you store it in the cookie and base64_decode the string stored in the cookie becore decrypting.

Example:

function setEncryptedCookie($cookieName, $data)
{
  setcookie($cookieName, base64_encode($this->encrypt($data)), time()+$this->expire); 
}

function getEncryptedCookie($cookieName)
{
  return $this->decrypt(base64_decode($_COOKIE[$cookieName]));
}
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0
eric at ez-llc dot com
8 years ago
I was able get php and perl to play together with blowfish using cipher block chaining.  The blowfish key needs to be atleast 8 chars (even though blowfish min is 8 bits, perl didn't like keys smaller than 8 chars) and max 56.  The iv must be exactly 8 chars and padding needs to be null because php pads with nulls.  Also, php needs libmcrypt >= 2.4.9 to be compatible with perl.

PERL
----

use Crypt::CBC;
$cipher = Crypt::CBC->new( {'key' => 'my secret key',
                                    'cipher'=> 'Blowfish',
                                    'iv' => '12345678',
                                    'regenerate_key' => 0,
                                    'padding' => 'null',
                                    'prepend_iv' => 0
                                    });
$cc = 'my secret text';
$encrypted = $cipher->encrypt($cc);
$decrypted = $cipher->decrypt($encrypted);

print "encrypted : ".$encrypted;
print "<br>";
print "decrypted : ".$decrypted;

PHP
---

$cc = 'my secret text';
$key = 'my secret key';
$iv = '12345678';

$cipher = mcrypt_module_open(MCRYPT_BLOWFISH,'','cbc','');

mcrypt_generic_init($cipher, $key, $iv);
$encrypted = mcrypt_generic($cipher,$cc);
mcrypt_generic_deinit($cipher);

mcrypt_generic_init($cipher, $key, $iv);
$decrypted = mdecrypt_generic($cipher,$encrypted);
mcrypt_generic_deinit($cipher);

echo "encrypted : ".$encrypted;
echo "<br>";
echo "decrypted : ".$decrypted;
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0
pauls at sellingsource dot com
11 years ago
If you are encrypting binary and there is a null terminator partway through your encryption, you will loose the rest of the string.  A workaround is to base64_encode your binary string first.

We found this problem while trying to encrypt CC information.  Some CC values would not decrypt after we converted them to a binary string.

We were using the MCRYPT_RIJNDAEL_256 module to encrypt with.

Hope this helps someone.
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