Case-Insensitive Passwords

The basic premise of my plugin is that it takes the password given to it and forces it to lowercase before hashing it and storing it in the database. When a user logs in, it will take the password input and force it to lowercase, hash it, and compare it to what is stored in the database. This produces the affect of case-insensitivity. The case-insensitivity only works for newly generated passwords, so I built the plugin to check the password submitted without forcing to lowercase, if it fails it will force it to lowercase and check again.