If you can achieve your password policy requirements by using the strong password check plug-in provided with Directory Server, do not write your own plug-in.
The strong password check plug-in provided with Directory Server can be configured for your deployment, checking the password quality aspects that you consider essential. You can configure the following:
The number of lowercase, uppercase, numeric, and special characters required in a password value
A special configuration setting also allows you to enforce a mix of characters.
The absence of prohibited strings, read from a dictionary file
You can use the default English-language file that is provided. Alternatively, you can add or substitute your own file.
These configuration settings are in addition to other checks. Such checks govern password length, whether the password matches common attributes on the entry, and so forth.
In many cases, you can avoid writing your own password check plug-in.