(PHP 4 >= 4.0.2)

mcrypt_get_iv_size -- Returns the size of the IV belonging to a specific cipher/mode combination


int mcrypt_get_iv_size (string cipher, string mode)

int mcrypt_get_iv_size (resource td)

The first prototype is when linked against libmcrypt 2.2.x, the second when linked against libmcrypt 2.4.x.

mcrypt_get_iv_size() returns the size of the Initialisation Vector (IV) in bytes. On error the function returns FALSE. If the IV is ignored in the specified cipher/mode combination zero is returned.

Cipher is one of the MCRYPT_ciphername constants of the name of the algorithm as string.

Mode is one of the MCRYPT_MODE_modename constants of one of "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".

Td is the algorithm specified.