I'm doing some basic work with cryptography right now, and I'm looking into different methods.

My teacher suggested using Riemann's zeta as a base, but I look at it and can't help but notice that it goes off to infinity.  I was wondering if anyone has any knowledge of how it would be used?

I currently use it by just taking it's limit, but I'm pretty sure it's not the most effective way...

O come on :\

Someone has to know!