mcrypt_create_iv() – Creating an Initialization Vector from a Random Source
The article explains how the PHP function mcrypt_create_iv() generates an initialization vector of a given size using various random sources, describes its parameters, default behavior, platform considerations, and return values, emphasizing that the IV need not be kept secret.
The mcrypt_create_iv() function generates an initialization vector (IV) of a specified size using a chosen random source.
An IV serves as a seed for encryption algorithms and does not need to be kept secret; it can be transmitted alongside the ciphertext without compromising security.
Parameters
size – The length of the IV to generate.
source (optional) – The source of random data. Acceptable values are MCRYPT_RAND (system RNG), MCRYPT_DEV_RANDOM (reads from /dev/random), and MCRYPT_DEV_URANDOM (reads from /dev/urandom). On Windows prior to PHP 5.3.0 only MCRYPT_RAND is supported.
Before PHP 5.6.0 the default value for source is MCRYPT_DEV_RANDOM.
Return value
Returns the generated IV as a string, or FALSE on failure.
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