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This document uses PHP Chinese website manual Release
(PHP 4 >= 4.0.2, PHP 5)
mcrypt_decrypt — 使用给定参数解密密文
$cipher
, string $key
, string $data
, string $mode
[, string $iv
] )
解密 data
并返回明文。
cipher
MCRYPT_ciphername
常量中的一个,或者是字符串值的算法名称。
key
数据加密密钥。
如果密钥长度不是加解密算法能够支持的有效长度,
那么会产生警告并且返回 FALSE
data
要使用给定的 cipher
和
mode
解密的数据。
如果数据大小不是 n * 分组大小,则在其后追加 '\0' 来补齐。
mode
MCRYPT_MODE_modename
常量中的一个,或以下字符串中的一个:"ecb","cbc","cfb","ofb","nofb" 和 "stream"。
iv
Used for the initialization in CBC, CFB, OFB modes, and in some algorithms in STREAM mode. If the provided IV size is not supported by the chaining mode or no IV was provided, but the chaining mode requires one, the function will emit a warning and return FALSE
.
以字符串格式返回解密后的数据, 或者在失败时返回 FALSE
。
版本 | 说明 |
---|---|
5.6.0 |
不再接受无效长度的 key and iv 参数。
如果参数长度无效,则 mcrypt_decrypt() 函数会产生警告并且返回 FALSE 。
之前版本中,对于长度不足的密钥和初始向量会在其后补齐 '\0'
使其达到有效长度。
|
[#1] artaxerxes2 at iname dot com [2013-05-21 16:17:58]
To decrypt data coming from MySQL's AES_ENCRYPT function:
<?php
function mysql_aes_key($key)
{
$new_key = str_repeat(chr(0), 16);
for($i=0,$len=strlen($key);$i<$len;$i++)
{
$new_key[$i%16] = $new_key[$i%16] ^ $key[$i];
}
return $new_key;
}
function aes_decrypt($encrypted,$key)
{
// if $encrypted is HEXed, then return it to binary
$encrypted = pack('H*',$encrypted);
$key = mysql_aes_key($key);
return rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128,$key,$encrypted,MCRYPT_MODE_ECB,''),"\x00..\x1F");
}
?>
adapted from the article "Replicating MySQL AES Encryption Methods With PHP" (dated 2012-05-20) found somewhere online.
[#2] beltrachi [2011-09-30 00:34:06]
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.
[#3] evangelion207 at hotmail dot com [2011-04-17 08:24:13]
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..
[#4] Anonymous [2010-11-24 03:41:27]
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);
?>
[#5] david at sickmiller dot com [2008-10-02 10:15:29]
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
?>
[#6] eddiec at stararcher dot com [2005-07-13 18:26:39]
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
?>