(PHP 4 >= 4.0.2, PHP 5, PHP 7)
mcrypt_get_iv_size — Returns the size of the IV belonging to a specific cipher/mode combination
$cipher
, string $mode
)
Gets the size of the IV belonging to a specific
cipher/mode combination.
It is more useful to use the mcrypt_enc_get_iv_size() function as this uses the resource returned by mcrypt_module_open().
cipherUma das constantes MCRYPT_ciphername, ou o nome do algoritmo como string.
modeUma das constantes MCRYPT_MODE_modename, ou uma das strings: "ecb", "cbc", "cfb", "ofb", "nofb" ou "stream".
The IV is ignored in ECB mode as this mode does not require it. You will need to have the same IV (think: starting point) both at encryption and decryption stages, otherwise your encryption will fail.
Returns the size of the Initialization Vector (IV) in bytes. On error the
function returns FALSE. If the IV is ignored in the specified cipher/mode
combination zero is returned.
Exemplo #1 mcrypt_get_iv_size() Example
<?php
echo mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB) . "\n";
echo mcrypt_get_iv_size('des', 'ecb') . "\n";
?>