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mcrypt_create_iv

(PHP3 >= 3.0.8, PHP4 )

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

Description

string mcrypt_create_iv (int size, int source)

Mcrypt_create_iv() is used to create an IV.

mcrypt_create_iv() takes two arguments, size determines the size of the IV, source specifies 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). If you use MCRYPT_RAND, make sure to call srand() before to initialize the random number generator.

Example 1. Mcrypt_create_iv() example


<?php
$cipher = MCRYPT_TripleDES;
$block_size = mcrypt_get_block_size ($cipher);
$iv = mcrypt_create_iv ($block_size, MCRYPT_DEV_RANDOM);
?>

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