This is not an improvement question, I am Searching for a wordpress plugin for Joomla that enables customers to login to some secure zone with universal qualifications that'll be supplied by admin. After signing in that user is going to be granted access and can have the ability to download private files.
Any assistance will be appreciated.
You'll need a component, not really a wordpress plugin. The term 'plugin' has special meaning in Joomla. See for a reason: http://docs.joomla.org/Extension_types_%28general_definitions%29
I recommend searching at something similar to DocMan: http://www.joomlatools.eu/products/docman