ERROR: could not find gem auth_generator-2.0.5.gem locally or in a repository

Hi community, I found a very interesting plugin called "auth_generator" and wanted to install it. So I downloaded the provided gem auth_generator-2.0.5.gem from the website and did this: $ sudo gem install auth_generator-2.0.5.gem which echoed this message: ERROR: could not find gem auth_generator-2.0.5.gem locally or in a repository

As I'm new to Ruby and to Rails I don't know if that is a mistake of mine or of the gem, but I hope you can help me to solve the problem.

Thank you very much in advance Christoph

Although this is more a ruby than a rails problem: Does anybody has an idea ?

Christoph