Registration passphrase for WordPress similar to JR Passphrase?

Hello all. I am wondering if anyone knows of a plugin or solution for WordPress that would allow us to restrict the ability to register to only those who have a passphrase we provide them. Being able to create multiple (even "unlimited") would be most desired.

There is an example of what we are looking for called JR Passphrase, but it is for Joomla. We are looking for a WordPress equivalent.

The Joomla one for reference is here:

http://www.rayonics.com/articles/35-joomla/56-jrpassphrase-comparison

http://www.rayonics.com/downloadpage?task=viewcategory&catid=11