php man page for mcrypt_create_iv

Query: mcrypt_create_iv

OS: php

Section: 3

Format: Original Unix Latex Style Formatted with HTML and a Horizontal Scroll Bar

MCRYPT_CREATE_IV(3)							 1						       MCRYPT_CREATE_IV(3)

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

SYNOPSIS
string mcrypt_create_iv (int $size, [int $source = MCRYPT_DEV_URANDOM])
DESCRIPTION
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.
PARAMETERS
o $size - The size of the IV. o $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 Win- dows. 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.
RETURN VALUES
Returns the initialization vector, or FALSE on error.
CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 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(3) first. | | | This is now done automatically. | | | | +--------+---------------------------------------------------+
EXAMPLES
Example #1 mcrypt_create_iv(3) Example <?php $size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB); $iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM); ?>
SEE ALSO
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(3). PHP Documentation Group MCRYPT_CREATE_IV(3)
Related Man Pages
urandom(7d) - sunos
mcrypt_encrypt(3) - php
mcrypt_create_iv(3) - php
hash_pbkdf2(3) - php
mdecrypt_generic(3) - php
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