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(PHP 4 >= 4.0.2, PHP 5, PHP 7 < 7.2.0, PECL mcrypt >= 1.0.0)



本函数已自 PHP 7.1.0 起废弃并将自 PHP 7.2.0 起移除。强烈建议不要使用本函数。


    string $algorithm,
    string $algorithm_directory,
    string $mode,
    string $mode_directory
): resource

本函数打开指定算法和模式对应的模块。 算法名称可以是字符串,例如 "twofish", 也可以是 MCRYPT_ciphername 常量。 调用 mcrypt_module_close() 函数可以关闭模块。



MCRYPT_ciphername 常量中的一个,或者是字符串值的算法名称。


algorithm_directory 参数指示加密模块的位置。 如果你提供此参数,则使用你指定的值。 如果将此参数设置为空字符串(""),将使用 php.ini 中的 mcrypt.algorithms_dir 。 如果不指定此参数,则使用 libmcrypt 的编译路径 (通常是 /usr/local/lib/libmcrypt)。


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"。


algorithm_directory 参数指示加密模式的位置。 如果你提供此参数,则使用你指定的值。 如果将此参数设置为空字符串(""),将使用 php.ini 中的 mcrypt.modes_dir 。 如果不指定此参数,则使用 libmcrypt 的编译路径 (通常是 /usr/local/lib/libmcrypt)。


成功则返回加密描述符,如果发生错误则返回 false


示例 #1 mcrypt_module_open() 示例

= mcrypt_module_open(MCRYPT_DES, '',
MCRYPT_MODE_ECB, '/usr/lib/mcrypt-modes');

$td = mcrypt_module_open('rijndael-256', '', 'ofb', '');

示例中的第一行从默认目录打开 DES 加密算法, 从 /usr/lib/mcrypt-modes 目录打开 ECB 模式。 第二个示例中,使用字符串形式表示算法和模式, 这种形式仅适用于 libmcrypt 2.4.x 或 2.5.x 版本。

示例 #2 在加密中使用 mcrypt_module_open()

/* 打开加密算法和模式 */
$td = mcrypt_module_open('rijndael-256', '', 'ofb', '');

/* 创建初始向量,并且检测密钥长度。
* Windows 平台请使用 MCRYPT_RAND。 */
$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_DEV_RANDOM);
$ks = mcrypt_enc_get_key_size($td);

/* 创建密钥 */
$key = substr(md5('very secret key'), 0, $ks);

/* 初始化加密 */
mcrypt_generic_init($td, $key, $iv);

/* 加密数据 */
$encrypted = mcrypt_generic($td, 'This is very important data');

/* 结束加密,执行清理工作 */

/* 初始化解密模块 */
mcrypt_generic_init($td, $key, $iv);

/* 解密数据 */
$decrypted = mdecrypt_generic($td, $encrypted);

/* 结束解密,执行清理工作,并且关闭模块 */

/* 显示文本 */
echo trim($decrypted) . "\n";


add a note

User Contributed Notes 7 notes

20 years ago
Doing a trim($decrypted) will remove the null padding that may occur as a result of decryption.

The problem is if you're encrypting something like a MSWord document which can commonly end with nulls. The result $decrypted will be smaller than the original cleartext - which will then fail to open in MSOffice.

To get around this, make sure you store the length of the original cleartext, and when you decrypt it, do:

$decrypted = substr(mdecrypt_generic($td, $encrypted), 0, $originalLength);
11 years ago
for errors like
' mcrypt_module_open(): Could not open encryption module in '

Make sure you're using the right name. The page giving the list of ciphers is NOT the right way to say each cipher (shown here

In order to see what ones are supported, try phpinfo(); and look under mcrypt to find something like this

mcrypt support => enabled
mcrypt_filter support => enabled
Version => 2.5.8
Api No => 20021217
Supported ciphers => cast-128 gost rijndael-128 twofish arcfour cast-256 loki97 rijndael-192 saferplus wake blowfish-compat des rijndael-256
serpent xtea blowfish enigma rc2 tripledes
Supported modes => cbc cfb ctr ecb ncfb nofb ofb stream
dinamic at gmail dot com
16 years ago
Also it should be pointed that md5() and/or sha1() should not be used while forming your key for the mcrypt. This is so because hex encoding uses a set of only 16 characters [0-9a-f], which is equivalent to 4 bits, and thus halve the strength of your encryption: 4 x 32 = 128-bit.

I have re-wrote the example shown, so here is my suggestion to get real 256-bit encryption:

= "this is a secret key";
$key2 = "this is the second secret key";
$input = "Let us meet at 9 o'clock at the secret place.";
$length = strlen($input);

/* Open the cipher */
$td = mcrypt_module_open('rijndael-256', '', 'cbc', '');

/* Create the IV and determine the keysize length, use MCRYPT_RAND
* on Windows instead */
$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_RAND);
$ks = mcrypt_enc_get_key_size($td);

/* Create key */
$key1 = md5($key1);
$key2 = md5($key2);

$key = substr($key1, 0, $ks/2) . substr(strtoupper($key2), (round(strlen($key2) / 2)), $ks/2);

$key = substr($key.$key1.$key2.strtoupper($key1),0,$ks);

/* Intialize encryption */
mcrypt_generic_init($td, $key, $iv);

/* Encrypt data */
$encrypted = mcrypt_generic($td, $input);

/* Terminate encryption handler */

/* Initialize encryption module for decryption */
mcrypt_generic_init($td, $key, $iv);

/* Decrypt encrypted string */
$decrypted = mdecrypt_generic($td, $encrypted);

/* Terminate decryption handle and close module */

/* Show string */
echo "Text: ".substr($decrypted,0,$length) . "<br>";
"Encoded: ".$encrypted ."<br>";
"<br>key1: $key1 <br>key2: $key2<br>created key: $key";
15 years ago
about the previous comments on hex formatting and capitalization as a way to improve the key:

this would seem pretty obvious, but it is a choice to be limited to only hex characters ([0-9a-z]); you can get the original RAW output from md5() or sha1() and not the default readable hex formatting.

the result of a raw output will be 16 o 20 (depending on the hash function being used) series of chars in the range 0-255. way better than [0-9a-z] and even [0-9a-zA-Z].

16 or 20 is generally lower than the maximum key lenght ($ks in the example), but you can append two or more keys together:

= 'something very secret';
$human_key2 = 'something else very secret';

// 40 bytes binary key using two "human readable" keys and sha1.
$bigger_binary_key = sha1($human_key1, true) . sha1($human_key2, true);

// then just use it as you would (extract taken from the example)
$key = substr($bigger_binary_key, 0, $ks);

... or you can automatically split one large "human key" into two or more parts, hash those parts with sha1 (raw output!) and merge them together again (in original order or rearrange, salt, transform them as you like) to get a binary key of 40, 60, 80 or more chars depending on the number of parts the secret key has been splitted =)
8 years ago
Follow up to anonymous with Windows' mcrypt_module_open() errors:

= mcrypt_list_modes();
$A = mcrypt_list_algorithms();
foreach (
$M as $m)
foreach (
$A as $a) {
$t = @mcrypt_module_open($a,'',$m,'');
"$m, $a = ";
print (

This will show that not all modes work with all algorithmns. Cygwin also has no 'libmcrypt.dll' and it too will work with only some combinations.

(First tries just happened to be one of the ones that did not work!)
14 years ago
Keep in mind that the mcrypt functions do not implement padding like e.g. pkcs#5. This causes the problem with zero bytes at the end and the sting cannot be correctly decoded in other environments.

For an example how to add pkcs 5 padding, see ref.mcrypt.php
15 years ago
A slight improvement of dinamic's function to create a key:

I think the weak point is that capitals are always used in the same part of the string. The following code capitalizes random characters of the string, making the key less predictable:

= substr($key1, 0, $ks/2) . substr($key2, (round(strlen($key2) / 2)), $ks/2);
$key = substr($key.$key1.$key2.$key1,0,$ks);

$buffer = str_split($key);

$limit = count($buffer)-1;
srand((float)microtime() * 1000000);

$end = rand(0, $limit);
$a = 0;

// replace random chars with capitals
while ($a < $end) {
$usec, $sec) = explode(' ', microtime());
$seed = ((float)$sec) + ((float) $usec * 100000);

$index = mt_rand(0,$limit);

$buffer[$index] = strtoupper($buffer[$index]);

$key = join('', $buffer);
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