Mcrypt
For those of you that need to use PKCS#5 padding, the mcrypt API’s for PHP do not support it. However, you can DIY using the following:
function encrypt_something ( $input )
<
$size = mcrypt_get_block_size ( ‘des’ , ‘ecb’ );
$input = pkcs5_pad ( $input , $size );
$key = ‘YOUR SECRET KEY HERE’ ;
$td = mcrypt_module_open ( ‘des’ , » , ‘ecb’ , » );
$iv = mcrypt_create_iv ( mcrypt_enc_get_iv_size ( $td ), MCRYPT_RAND );
mcrypt_generic_init ( $td , $key , $iv );
$data = mcrypt_generic ( $td , $input );
mcrypt_generic_deinit ( $td );
mcrypt_module_close ( $td );
$data = base64_encode ( $data );
return $data ;
>
function pkcs5_pad ( $text , $blocksize )
<
$pad = $blocksize — ( strlen ( $text ) % $blocksize );
return $text . str_repeat ( chr ( $pad ), $pad );
>
function pkcs5_unpad ( $text )
<
$pad = ord ( $text < strlen ( $text )- 1 >);
if ( $pad > strlen ( $text )) return false ;
if ( strspn ( $text , chr ( $pad ), strlen ( $text ) — $pad ) != $pad ) return false ;
return substr ( $text , 0 , — 1 * $pad );
>
?>
mysql AES_ENCRYPT() compatibly function for PHP :
function mysql_aes_encrypt ( $val , $ky ) <
$mode = MCRYPT_MODE_ECB ;
$enc = MCRYPT_RIJNDAEL_128 ;
$val = str_pad ( $val , ( 16 *( floor ( strlen ( $val ) / 16 )+( strlen ( $val ) % 16 == 0 ? 2 : 1 ))), chr ( 16 -( strlen ( $val ) % 16 )));
return mcrypt_encrypt ( $enc , $ky , $val , $mode , mcrypt_create_iv ( mcrypt_get_iv_size ( $enc , $mode ), MCRYPT_DEV_URANDOM ));
>
?>
Please note that if the strlen($ky)>16 then this function will not be compatible.
If you’ve ever compiled PHP from source (any version) you may be familiar with the [in]famous MCRYPT_BLOWFISH_128 compilation error that appears when you attempt to compile —with-mcrypt. It occurs often on Debian but not only there. The problem: during compilation, the PHP configure script always assumes that libmcrypt has been built in conjunction with libltdl. Whenever that is not the case, PHP compilation will fail later saying certain headers (such as the above blowfish example) are missing from mcrypt.h (which is misleading, they’re not supposed to be there nor looked after if libltdl was properly involved). Solution: make sure your libmcrypt was linked against libltdl before you even start configuring PHP. You can check by running ‘ldd lybmcrypt.so’ and verifying that libltdl appears in the output. libltdl can be found in libltld[3][-dev] on Debian or in libtool-libs on Red Hat.
if you don’t have mcrypt installed, try phpseclib — http://phpseclib.sourceforge.net
includes pure-php implementations of des, 3des, rc4, aes, and rijndael. uses mcrypt if it’s available and a pure-php implementation otherwise. it also has the distinction of having the fastest existent pure-php aes implementation as per section 3.5.5. «Speed Comparisons» of the documentation.
Regarding storing the result on a postgres DB that uses Unicode (follow up to a post below).
You don’t need to change the DB’s encoding to ASCII.
Simply use BASE64 to encode the result, it’s perfectly safe.
use base64_decode before you decrypt.
— Tomer Levinboim
mcrypt_ecb with base64_decode gave some problems, i found out that it had to be chopped to work:
chop ( mcrypt_ecb ( MCRYPT_BLOWFISH , $key , base64_decode ( $input ), MCRYPT_DECRYPT ));
?>
when compiling php —with-mcrypt, phpinfo() says, that mcrypt ist enabled, but
«Supported ciphers none» and
«Supported modes none»
In order to get mcrypt to work in php, you have to configure and compile the libmcrypt source package with the following options:
./configure —disable-posix-threads —enable-dynamic-loading
DEBIAN users: avoid mcrypt installation headaches.
to add mcrypt support to an existing php installation, get root and run
apt-get install php4-mcrypt
restart your webserver, and voila.
If you compiled mcrypt and php without problem, but phpinfo() shows there are no supported ciphers and modes, try to change mode to 755 on libdirs (/usr/local/libmcrypt, /usr/local/libcrypt).
This works completely with mysql aes, even long keys.
function mysql_aes_decrypt ( $val , $ky )
<
$key = «\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0» ;
for( $a = 0 ; $a < strlen ( $ky ); $a ++)
$key [ $a % 16 ]= chr ( ord ( $key [ $a % 16 ]) ^ ord ( $ky [ $a ]));
$mode = MCRYPT_MODE_ECB ;
$enc = MCRYPT_RIJNDAEL_128 ;
$dec = @ mcrypt_decrypt ( $enc , $key , $val , $mode , @ mcrypt_create_iv ( @ mcrypt_get_iv_size ( $enc , $mode ), MCRYPT_DEV_URANDOM ) );
return rtrim ( $dec ,(( ord ( substr ( $dec , strlen ( $dec )- 1 , 1 ))>= 0 and ord ( substr ( $dec , strlen ( $dec )- 1 , 1 ))>
function mysql_aes_encrypt ( $val , $ky )
<
$key = «\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0» ;
for( $a = 0 ; $a < strlen ( $ky ); $a ++)
$key [ $a % 16 ]= chr ( ord ( $key [ $a % 16 ]) ^ ord ( $ky [ $a ]));
$mode = MCRYPT_MODE_ECB ;
$enc = MCRYPT_RIJNDAEL_128 ;
$val = str_pad ( $val , ( 16 *( floor ( strlen ( $val ) / 16 )+( strlen ( $val ) % 16 == 0 ? 2 : 1 ))), chr ( 16 -( strlen ( $val ) % 16 )));
return mcrypt_encrypt ( $enc , $key , $val , $mode , mcrypt_create_iv ( mcrypt_get_iv_size ( $enc , $mode ), MCRYPT_DEV_URANDOM ));
>
?>
the encrypted result data maybe binary data and It make errors in sql query.
so use the base64_encode/base64_decode function with mcrypt()
try below
base64_encode ( mcrypt_ecb ( MCRYPT_BLOWFISH , $key , $input , MCRYPT_ENCRYPT ));
mcrypt_ecb ( MCRYPT_BLOWFISH , $key , base64_decode ( $input ), MCRYPT_DECRYPT );
?>
mcrypt module initialization failed
I found this circumstance:
usemcrypt.php:
function protect () <
//some mcrypt/decrypt command
>
?>
filea.php:
include_once( ‘usemcrypt.php’ );
function a () <
protect ();
> ?>
fileb.php
function b () <
include_once( ‘usemcrypt.php’ );
protect ();
>
?>
filea.php and a() work fine
fileb.php and b() will report a mcrypt module initialization failed
I am assuming you can’t pull that module in on the fly. If you use a file that calls mcrypt, it has to be included at the head, not in a function.
The follow function is a implementation of the RC4 cypher algorithm in pure PHP code.
The function is used to encrypt and decrypt data.
/**
* Crypt/decrypt strings with RC4 stream cypher algorithm.
*
* @param string $key Key
* @param string $data Encripted/pure data
* @see http://pt.wikipedia.org/wiki/RC4
* @return string
*/
function rc4 ( $key , $data )
// Store the vectors «S» has calculated
static $SC ;
// Function to swaps values of the vector «S»
$swap = create_function ( ‘&$v1, &$v2’ , ‘
$v1 = $v1 ^ $v2;
$v2 = $v1 ^ $v2;
$v1 = $v1 ^ $v2;
‘ );
$ikey = crc32 ( $key );
if (!isset( $SC [ $ikey ])) // Make the vector «S», basead in the key
$S = range ( 0 , 255 );
$j = 0 ;
$n = strlen ( $key );
for ( $i = 0 ; $i < 255 ; $i ++) $char = ord ( $key < $i % $n >);
$j = ( $j + $S [ $i ] + $char ) % 256 ;
$swap ( $S [ $i ], $S [ $j ]);
>
$SC [ $ikey ] = $S ;
> else $S = $SC [ $ikey ];
>
// Crypt/decrypt the data
$n = strlen ( $data );
$data = str_split ( $data , 1 );
$i = $j = 0 ;
for ( $m = 0 ; $m < $n ; $m ++) $i = ( $i + 1 ) % 256 ;
$j = ( $j + $S [ $i ]) % 256 ;
$swap ( $S [ $i ], $S [ $j ]);
$char = ord ( $data [ $m ]);
$char = $S [( $S [ $i ] + $S [ $j ]) % 256 ] ^ $char ;
$data [ $m ] = chr ( $char );
>
return implode ( » , $data );
>
?>
To enable mcrypt extension under Windows you need to:
1) uncomment line «extension=php_mcrypt.dll» in php.ini
2) download libmcrypt.dll from http://files.edin.dk/php/win32/mcrypt/ and put it to System32 directory (for example C:\Windows\System32).
Tested on Windows XP+Apache 1.3.37+PHP 4.4.6 (as SAPI module. )
P.S.
I wrote this because I got «Cannot load mcrypt extension. Please check your PHP configuration.» from phpMyAdmin when I simply uncommented «extension=php_mcrypt.dll» line.
If you plan to use Mcrypt Encryption to store encrypted data (e.g. passwords) in a (MySQL) database make sure to set the column to BLOB rather than VARCHAR. Otherwise the data may change which can give unexpected results if you decrypt the value.
After benchmarking AES in 256-bit operation, I’ve concluded that CBC is far faster than OFB. Using a 14.9 MiB file, on average.
Encrypt in CBC: 1.9 seconds
Encrypt in OFB: 45.7 seconds (same as CFB)
Just reading the file: ~.53 seconds
After some research, I’ve concluded that OFB and CFB are slightly more secure than CBC, however I believe the performance difference to be due to an implementation issue.
As a side note on ECB: As stated in the wiki linked to below, ECB is wholly inadequate. It not use an IV (whether it was supplied ot MCrypt or not), meaning the same key and plaintext always produce the same ciphertext and it doesn’t hide patterns. The site shows an excellent example of this.
If you’re going to encrypt data with something like this and store it in postgres.
function encrypt ( $string , $key ) <
$result = » ;
for( $i = 1 ; $i $char = substr ( $string , $i — 1 , 1 );
$keychar = substr ( $key , ( $i % strlen ( $key ))- 1 , 1 );
$char = chr ( ord ( $char )+ ord ( $keychar ));
$result .= $char ;
>
return $result ;
>
?>
Make sure when you create your database to set the encoding to SQL_ASCII because you won’t be able to store this data in a database that uses UNICODE
A further note for those doing interop between PHP and Java:
If you’re using the BouncyCastle library on the Java side, then you can use the ZeroBytePadding mode now available in it. Mcrypt pads the data with Nulls rather than spaces.
I’ve sucessfully done interop using Blowfish/CBC/ZeroBytePadding between PHP and Java this way.
I’ve spent the majority of the day attempting to get mcrypt to work under IIS6 with Windows Server 2003 (Web Edition) and PHP 5.0.4
There seems to be some incompatability with enabling certain extensions (mcrypt being one) when you are running PHP as ISAPI in this environment.
The way to solve the problem (the error will be that it cannot load php_mcrypt.dll — access is denied) is to run in CGI. While this isn’t supposed to be as good performance wise, if you need the mcrypt support (or Oracle support, too, I believe) then this is the only way I’ve found to do it.
Attention when using keys longer than the actual key size (i.e. 160 bit instead of 128 bit).
It will work inbetween PHP scripts, but might cause problems when using openssl or other packages with this integration of mcrypt. Cut them always to the supported size (mcrypt_enc_get_key_size) to avoid sleepless hours.
If you are using ECB mode to encrypt it does not seem to use the iv (initialization vector) for much of anything, given the same key it will always decrypt it no matter what the iv is. If you use CBC mode you must decrypt with the same iv that you encrypted with.
If you use a different iv before decrypting, your decrypt will not work. IMHO it seems better to use CBC mode than ECB as ECB will always encrypt to the same cipher text given the same plain text (leaving you open to know plaintext attacks). CBC uses the random iv which means text encrypts to different things. You probably could get the same effect from using random keys in ECB mode.
Read that in the Schneier book — Applied Cryptography (ISBN 0-471-11709-9) This book is a must for anyone seriously using any type of encryption.
The Pear class Crypt/Blowfish.php will use the mcrypt module if available but the mcrypt module is not required.
Some very easy Pear and example pseudocode to protect your data by encrypting your databases with a one-way hash and blowfish symmetric encryption.
http://en.wikibooks.org/wiki/Cryptography/Database_protection
Using a one-way hash and blowfish symmetric encryption.
1. Insert a record of John Doe in an encrypted database.
2. Get the encrypted record of user John Doe and decrypt the data.
1. Insert a record of John Doe in an encrypted database.
require_once( «Crypt/Blowfish.php» ); // a Pear class
$aRecord [ ’email’ ] = «johndoe@anisp.localhost» ; // The Primary key
$aRecord [ ‘name’ ] = «John Doe» ;
$aRecord [ ‘creditnr’ ] = «0192733652342» ;
// crypt — one-way encryption
$cipher_key = crypt ( $aRecord [ ’email’ ] , «AN_SECRET_COMPANY_SALT» );
$bf = new Crypt_Blowfish ( ‘ecb’ );
$bf -> setKey ( $cipher_key );
// crypt_blowfish symmetric encryption to encrypt the data
$aRecord [ ’email’ ] = $bf -> encrypt ( $aRecord [ ’email’ ] );
$aRecord [ ‘name’ ] = $bf -> encrypt ( $aRecord [ ‘name’ ] );
$aRecord [ ‘creditnr’ ] = $bf -> encrypt ( $aRecord [ ‘creditnr’ ] );
$result = sqlInsert ( $aRecord ) ;
?>
2. Get the encrypted record of user John Doe and decrypt the data.
require_once( «Crypt/Blowfish.php» ); // a Pear class
// crypt — one-way encryption
$cipher_key = crypt ( $primary_key , «AN_SECRET_COMPANY_SALT» );
$bf = new Crypt_Blowfish ( ‘ecb’ );
$bf -> setKey ( $cipher_key );
// crypt_blowfish symmetric encryption to ecrypt the primary key for a sql select
$select_key = $bf -> encrypt ( $primary_key ) ;
$aRecord = sqlSelectWithPKEY ( $select_key );
// crypt_blowfish symmetric encryption to decrypt the data
$aRecord [ ’email’ ] = $bf -> decrypt ( $aRecord [ ’email’ ] );
$aRecord [ ‘name’ ] = $bf -> decrypt ( $aRecord [ ‘name’ ] );
$aRecord [ ‘creditnr’ ] = $bf -> decrypt ( $aRecord [ ‘creditnr’ ] );
?>
Thanks for reading this.