mcrypt_get_iv_size

(PHP 4 >= 4.0.2, PHP 5)

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

Description

int mcrypt_get_iv_size ( string $cipher , string $mode )

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 or one of "ecb", "cbc", "cfb", "ofb", "nofb" or "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.

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

Пример #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";
?>

Коментарии

Jun 28

Автор: Hernanibus


The size of the initialization vector (iv) will be returned in bytes NOT bits, something to keep in mind specially if the iv is passed together appended or prepended with the encrypted data for decryption

2016-06-28 08:45:53

http://php5.kiev.ua/manual/ru/function.mcrypt-get-iv-size.html

mcrypt_get_cipher_name

mcrypt_get_key_size

mcrypt

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