openssl_cipher_iv_length

(PHP 5 >= 5.3.3, PHP 7)

openssl_cipher_iv_lengthGets the cipher iv length

Beschreibung

int openssl_cipher_iv_length ( string $method )

Gets the cipher initialization vector (iv) length.

Parameter-Liste

method

The cipher method, see openssl_get_cipher_methods() for a list of potential values.

R√ľckgabewerte

Returns the cipher length on success, or FALSE on failure.

Fehler/Exceptions

Emits an E_WARNING level error when the cipher algorithm is unknown.

Beispiele

Beispiel #1 openssl_cipher_iv_length() example

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

echo 
$ivlen;
?>

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

16
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User Contributed Notes 2 notes

up
7
Tim Hunt
3 years ago
The return value is a length in bytes. (Not bits, or anything else.)
up
0
Vee W.
15 days ago
<?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.
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