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
This function was DEPRECATED in PHP 7.1.0, and REMOVED in PHP 7.2.0.
Alternatives to this function include:
Description
$size
[, int $source
= MCRYPT_DEV_URANDOM
] ) : stringCreates 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
-
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) andMCRYPT_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.
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() first. This is now done automatically. |
Examples
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);
?>
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() - Generates cryptographically secure pseudo-random bytes
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Document created the 30/01/2003, last modified the 26/10/2018
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