php 한글 메뉴얼 도움말 검색 사이트 Creates an initialization vector (IV) from a random source [function.mcrypt-create-iv]

설명

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

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.

인수

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.

Note: Note that MCRYPT_DEV_RANDOM may block until more entropy is available.

반환값

Returns the initialization vector, or FALSE on error.

변경점

버전	설명
5.6.0	`MCRYPT_DEV_URANDOM` is now the default value of `source`.
5.3.0	`MCRYPT_DEV_RANDOM` and `MCRYPT_DEV_URANDOM` became available on Windows platforms.
5.3.0	It is no longer required to call srand() first. This is now done automatically.

예제

Example #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);
?>

참고

» 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() - Generates cryptographically secure pseudo-random bytes