mcrypt_create_ivPHP ManualPrevNextmcrypt_create_ivmcrypt_create_iv -- Create an initialization vector (IV) from a random sourceDescriptionstring 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 1  2 <?php 3 $cipher = MCRYPT_TripleDES; 4 $block_size = mcrypt_get_block_size($cipher); 5 $iv = mcrypt_create_iv($block_size, MCRYPT_DEV_RANDOM); 6 ?> 7  PrevHomeNextmcrypt_get_key_sizeUpmcrypt_cbc