Php/docs/function.mcrypt-create-iv

• PHP Manual
• Mcrypt 関数
• Creates an initialization vector (IV) from a random source

mcrypt_create_iv

(PHP 4, PHP 5, PHP 7 < 7.2.0, PECL mcrypt >= 1.0.0)

mcrypt_create_iv — Creates an initialization vector (IV) from a random source

警告 この関数は PHP 7.1.0 で 非推奨 となり、 PHP 7.2.0 で削除 されました。

この関数の代替として、これらが使えます。

• random_bytes()

説明

mcrypt_create_iv ( int $size [, int $source = MCRYPT_DEV_URANDOM ] ) : string

Creates an initialization vector (IV) from a random source.

The IV is only meant to give an alternative seed to the encryption routines. This IV does not need to be secret at all, though it can be desirable. You even can send it along with your ciphertext without losing security.

パラメータ

size

The size of the IV.

source

The source of the IV. The source can be MCRYPT_RAND (system random number generator), MCRYPT_DEV_RANDOM (read data from /dev/random) and MCRYPT_DEV_URANDOM (read data from /dev/urandom). Prior to 5.3.0, MCRYPT_RAND was the only one supported on Windows.

Note that the default value of this parameter was MCRYPT_DEV_RANDOM prior to PHP 5.6.0.

注意:

Note that MCRYPT_DEV_RANDOM may block until more entropy is available.

返り値

Returns the initialization vector, or false on error.

例

例1 mcrypt_create_iv() Example

<?php    $size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB);    $iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);?>

参考

• » http://www.ciphersbyritter.com/GLOSSARY.HTM#IV
• » http://www.quadibloc.com/crypto/co0409.htm
• Chapter 9.3 of Applied Cryptography by Schneier (ISBN 0-471-11709-9)
• random_bytes() - 暗号論的に安全な、疑似ランダムなバイト列を生成する