Mixture Generation vs. Moduler Exponantion Approach?

[Jenjen <jsong@aig.com>]

Recently I learned a new crypto algorithm--RPK (see www.rpk.co.nz).
It's based on mixture generator (MG) approach and claims much faster
than all existing public-key crypto-algorithms. But some people argue
that MG is not much different from moduler exponantiation (ME) approach,
which has been used in some existing crypto-algorithms. Therefore, RPK
may not be that much faster than others.

I'm new in this field and not sure whether these 2 approaches (Mixture
Generation vs. Moduler Exponantiation) are very different or not?
Can MG be much faster than ME or no much difference?
Would you help me with these questions or point me to a right direction?
I'd appreciate your help.