openssl_cipher_iv_length()

(PHP 5 >= 5.3.3, PHP 7)

获取密码iv长度

说明

openssl_cipher_iv_length(string $method): int

获取密码初始化向量(iv)长度。

参数

$method

密码的方法，更多值查看openssl_get_cipher_methods()函数。

返回值

成功，返回密码长度,失败返回FALSE.

错误／异常

当密码方法未知时，抛出一个E_WARNING级的错误。

范例

openssl_cipher_iv_length()范例

<?php
$method = 'AES-128-CBC';
$ivlen = openssl_cipher_iv_length($method);
echo $ivlen;
?>

以上例程的输出类似于：

16

The return value is a length in bytes. (Not bits, or anything else.)

<?php
$ciphers = openssl_get_cipher_methods();
//ECB mode should be avoided
$ciphers = array_filter($ciphers, function ($n) {
  return stripos($n, "ecb") === FALSE;
});
  
// At least as early as Aug 2016, Openssl declared the following weak: RC2, RC4, DES, 3DES, MD5 based
$ciphers = array_filter($ciphers, function ($c) {
  return stripos($c, "des") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
  return stripos($c, "rc2") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
  return stripos($c, "rc4") === FALSE;
});
$ciphers = array_filter($ciphers, function ($c) {
  return stripos($c, "md5") === FALSE;
});
if (is_array($ciphers)) {
  foreach ($ciphers as $cipher) {
    echo $cipher.': ';
    echo openssl_cipher_iv_length($cipher);
    echo "<br>\n";
  }
}
?>
Will be...
AES-xxx-xxx is 16
BF-xxx is 8
CAMELLIA-xxx is 16
CAST5-xxx is 8
IDEA-xxx is 8
SEED-xxx is 16
lower case:
aes-xxx-xxx are mixed between 16 and 12.
id-aes-xxx are mixed between 12 and 8.
The values above are tested with PHP 5.5 - 5.6 on Windows. In PHP 7.x is different than this.