mcrypt_create_iv
Caution, MCRYPT_RIJNDAEL_256 is not equivalent to AES_256.
The way to make RIJNDAEL be decrypted from AES with openssl is to use MCRYPT_RIJNDAEL_128 and padd the string to encrypt before encrypting with the follwing function:
<?php
function pkcs5_pad ($text, $blocksize) {
$pad = $blocksize - (strlen($text) % $blocksize);
return $text . str_repeat(chr($pad), $pad);
}
?>
On the decryption, the choosing of AES_256 or AES_128, etc. is based on the keysize used in the crypting. In my case it was a 128bit key so I used AES_128.
mcrypt_decrypt
(PHP 4 >= 4.0.2, PHP 5)
mcrypt_decrypt — Desencripta texto cifrado con los parámetros dados
Descripción
string mcrypt_decrypt
( string
$cipher
, string $key
, string $data
, string $mode
[, string $iv
] )
Desencripta data y devuelve los datos sin cifrar.
Parámetros
-
cipher -
Una de las constantes
MCRYPT_nombredelcifrado, o el nombre del algoritmo como string. -
key -
La clave con la cual los datos fueron encriptados. Si es más pequeña de lo requerido, se rellena con '\0'.
-
data -
La información que será descifrada con el cifrador y modo dados por los parámetros
cipherymode. Si el tamaño de la información no es n * blocksize, la información será rellenada con '\0'. -
mode -
Una de las constantes
MCRYPT_MODE_nombredelmodo, o una de las siguientes strings: "ecb", "cbc", "cfb", "ofb", "nofb" o "stream". -
iv -
Utilizado para la inicialización en los modos CBC, CFB, OFB, y en algunos algoritmos en modo STREAM. Si no se proporciona un IV, aunque es necesario para el algoritmo, la función lanza un mensaje de advertencia y utiliza un IV con todos sus bytes establecidos a "\0".
Valores devueltos
Devuelve los datos desencriptados en formato cadena.
add a note
User Contributed Notes
mcrypt_decrypt - [7 notes]
beltrachi ¶
1 year ago
evangelion207 at hotmail dot com ¶
2 years ago
Be careful, sometimes mcrypt_decrypt return additional white spaces to the uncrypted string; use trim() for deleting them. I was like 2 hours searching the error and it was that..
david at sickmiller dot com ¶
4 years ago
If you happen to be decrypting something encrypted in ColdFusion, you'll discover that its encrypt function apparently pads the plaintext with ASCII 4, the "end of transmission" character.
Building on eddiec's code, you can remove both nulls and EOTs with this:
<?php
$retval = mcrypt_decrypt( ...etc ...);
$retval = rtrim($retval, "\0\4"); // trim ONLY the nulls and EOTs at the END
?>
eddiec at stararcher dot com ¶
7 years ago
It appears that mcrypt_decrypt pads the *RETURN STRING* with nulls ('\0') to fill out to n * blocksize. For old C-programmers, like myself, it is easy to believe the string ends at the first null. In PHP it does not:
strlen("abc\0\0") returns 5 and *NOT* 3
strcmp("abc", "abc\0\0") returns -2 and *NOT* 0
I learned this lesson painfully when I passed a string returned from mycrypt_decrypt into a NuSoap message, which happily passed the nulls along to the receiver, who couldn't figure out what I was talking about.
My solution was:
<?php
$retval = mcrypt_decrypt( ...etc ...);
$retval = rtrim($retval, "\0"); // trim ONLY the nulls at the END
?>
Anonymous ¶
2 years ago
To remove PKCS7 padding:
<?php
$decrypted = mdecrypt_generic($td, base64_decode($enc_auth_token));
$dec_s = strlen($decrypted);
$padding = ord($decrypted[$dec_s-1]);
$decrypted = substr($decrypted, 0, -$padding);
?>
smp_info at yahoo dot com ¶
5 years ago
Since the returned data seems to be still padded with extra characters, you can get *only* the original data that was encrypted by str_replace()'ing the \x0 characters.
<?php
$decryptedData = str_replace("\x0", '', $encryptedData);
?>
maciej at wiercinski dot net ¶
2 years ago
If you want to combine mcrypt with MySQL's AES_DECRYPT / AES_ENCRYPT function, please keep in mind that it uses PKCS5 padding (code from note above works just fine), what is not mentioned in MySQL's documentation at all.