openssl_cipher_iv_length

(PHP 5 >= 5.3.3, PHP 7, PHP 8)

openssl_cipher_iv_length — Obtener la longitud del iv de cipher

Descripción

openssl_cipher_iv_length(string $method): int

Obtiene la longitud del vector de inicialización (iv) de cipher.

Parámetros

method: El método de cipher, véase openssl_get_cipher_methods() para una lista de valores potenciales.

Valores devueltos

Devuelve la longitud de cipher en caso de éxito, o false en caso de error.

Errores/Excepciones

Emite un error de nivel E_WARNING cuando el algoritimo de cipher es desconocido.

Ejemplos

Ejemplo #1 Ejemplo de openssl_cipher_iv_length()

<?php
$método = 'AES-128-CBC';
$longitud_iv = openssl_cipher_iv_length($método);

echo $longitud_iv;
?>

El resultado del ejemplo sería algo similar a:

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User Contributed Notes 2 notes

down

Tim Hunt ¶

9 years ago

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

down

-3

Vee W. ¶

6 years 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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