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.
The size of the IV.
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.
Returns the initialization vector, or FALSE
on error.
MCRYPT_DEV_URANDOM
source
MCRYPT_DEV_RANDOM
MCRYPT_DEV_URANDOM
It is no longer required to call srand() first. This is now done automatically.
<?php $size = mcrypt_get_iv_size(MCRYPT_CAST_256, MCRYPT_MODE_CFB); $iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM); ?>
» http://www.ciphersbyritter.com/GLOSSARY.HTM#IV -
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