mcrypt_decrypt

(PHP 4 >= 4.0.2, PHP 5)

mcrypt_decrypt — Belirtilen değiştirgelerle şifreli bir metnin şifresini çözer

Açıklama

string mcrypt_decrypt ( string $şifre , string $anahtar , string $veri , string $kip [, string $iv ] )

Belirtilen verinin şifresini çözer ve şifrelenmemiş dizgeyi döndürür.

Değiştirgeler

şifre: MCRYPT_şifre_adı sabitlerinden biri veya bir dizge olarak bir algoritma ismi.
key: Veriyi şifrelemekte kullanılan anahtar. Gereken anahtar uzunluğundan kısaysa dolgu olarak "\0" karakteri kullanılır.
data: Belirtilen şifre ve kip ile şifresi çözülecek veri. Verinin küme boyunun katları uzunlukta olmasını sağlamak için dolgu olarak "\0" karakteri kullanılır.
mode: MCRYPT_kip_adı sabitlerinden biri veya bir dizge olarak şunlardan biri: "ecb", "cbc", "cfb", "ofb", "nofb", "stream".
iv: CBC, CFB, OFB kiplerini ve STREAM kipindeki bazı algoritmaları ilklendirmek için kullanılan ilklendirme vektörü (IV). Bir IV belirtmezseniz tüm baytları "\0" karakterlerinden oluşan bir dizge kullanılır.

Dönen Değerler

Şifresi çözülmüş veriyi bir dizge olarak döndürür.

mcrypt_ecb

mcrypt_create_iv

[edit] Last updated: Fri, 23 Mar 2012

add a note User Contributed Notes mcrypt_decrypt

beltrachi 30-Sep-2011 12:34


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.

evangelion207 at hotmail dot com 17-Apr-2011 08:24


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..

maciej at wiercinski dot net 09-Apr-2011 12:59


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.

Anonymous 24-Nov-2010 03:41


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);


?>

david at sickmiller dot com 02-Oct-2008 10:15


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

?>

smp_info at yahoo dot com 10-Oct-2007 11:27


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);

?>

eddiec at stararcher dot com 13-Jul-2005 06:26


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


?>

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