Choosing Cryptographically Secure Token Generation Methods

The current practice of using md5(uniqid(mt_rand(), true)) to generate API access tokens has security concerns due to its dependency on the system clock and predictability. As a more robust solution, openssl_random_pseudo_bytes is recommended for its enhanced protection against prediction.

Equivalent Code and Length Considerations

The equivalent code utilizing openssl_random_pseudo_bytes is:

$token = bin2hex(openssl_random_pseudo_bytes(16));

For PHP 7 and above, the following syntax is also available:

$token = bin2hex(random_bytes(16));

The optimal length for the random string depends on the desired security level and the sensitivity of the data being protected. For most cases, a length of 16 bytes (128 bits) is considered sufficient. However, for highly sensitive applications, a longer length may be recommended.