This is an educational simulator tool which explores the Montgomery reduction algorithm. Commonly known as Montgomery multiplication, this algorithm is used to speed up modular exponentiation: a common operation in cryptography. The Overview section explains the algorithm and it's tradeoffs. A JAVA based simulator can be used to explore the efficiency of this method versus the square and multiply method.
Follow the Overview tab to learn about the Montgomery method. The Simulator tab will launch a JAVA applet. If you are unsure which fields to change, head over to the Tutorial tab for some info.