PHP Manual: Gets the key size of the specified cipher

int mcrypt_get_key_size ( int $cipher )

int mcrypt_get_key_size ( string $cipher , string $mode )

The first prototype is when linked against libmcrypt 2.2.x, the second when linked against libmcrypt 2.4.x or 2.5.x.

mcrypt_get_key_size is used to get the size of a key of the specified cipher (in combination with an encryption mode).

It is more useful to use the mcrypt_enc_get_key_size function as this uses the resource returned by mcrypt_module_open.

cipher: One of the MCRYPT_ciphername constants, or the name of the algorithm as string.
mode: One of the MCRYPT_MODE_modename constants, or one of the following strings: "ecb", "cbc", "cfb", "ofb", "nofb" or "stream".

Returns the maximum supported key size of the algorithm in bytes or FALSE on failure.

Example #1 mcrypt_get_key_size Example


<?php
    echo mcrypt_get_key_size('tripledes', 'ecb');
?>

The example above shows how to use this function when linked against libmcrypt 2.4.x or 2.5.x.

The above example will output:

mcrypt_get_key_size