Bukkit

The first thing to do is add the latest version of Shivtr Auth to your libraries. You will then want to get access to Shivtr Auth I recommend the code below.

private ShivtrAuth getShivtrAuth() {
    Plugin plugin = getServer().getPluginManager().getPlugin("Shivtr Auth");
 
    // Shivtr Auth may not be loaded
    if (plugin == null || !(plugin instanceof ShivtrAuth)) {
        return null; // Maybe you want throw an exception instead
    }
 
    return (ShivtrAuth) plugin;
}

Once you have this you will likely then want to grab the AuthenticationCore. To do this use the following code:

private AuthenticationCore auth;

auth = getShivtrAuth().getAuthenticationCore();

Instead you could do more of a Vault like usage and create a void which attempts to get the AuthenticationCore. Possibly like this:

private AuthenticationCore auth;

private void setUpAuthenticationCore() {
    Plugin plugin = getServer().getPluginManager().getPlugin("Shivtr Auth");
 
    // Shivtr Auth may not be loaded
    if (plugin == null || !(plugin instanceof ShivtrAuth)) {
        return; // Maybe you want throw an exception instead
    }

    auth = ((ShivtrAuth) plugin).getAuthenticationCore();
}

Once you do this you can then use any of the following functions.

Returns true if the player is on one of the list.

isValidCharacter(player);

Updates the Characters List.

updateCharacterLists();