With the release of Joomla! 3.2, the CMS introduced a new feature called, Strong Passwords. The intent was to enhance the encryption of password hashing and storage through the use of BCrypt, thus increasing the security of Joomla! 3.2 user accounts. Bcrypt was not available in the early releases of php 5.3, and with the first releases a bug in the algorithm surfaced. This prompted a change in the later php versions to fix it.
The Joomla 3 series required a minimum php version of 5.3+ which unfortunately includes php versions without BCrypt and the buggy first release of BCrypt. The Strong Passwords feature has built in compatibility to determine if BCrypt was available based on a php version check of the Joomla installation's server. The version check is used to determine exactly what the Strong Passwords feature would enable, BCrypt or the next best available password hashing encryption available. Unfortunately, this can lead to access issues under certain circumstances.
This is recommended if you are:
Your website will now no longer use the Strong Passwords feature to hash and store passwords.