Working Examples

This section provides working examples of the authentication and encryption
processes detailed in this chapter. The detail of the encryption and security process and
maths involved may be illustrated by an attractive analogy taken from Simon Singh’s
The Code Book, published by Fourth Estate (ISBN 1-857-02889-9).
The problem is to be able to transfer messages securely through an unsecure environment.
Suppose person Aand person B wish to communicate through the postal service.
Person A puts his message in a box and attaches a padlock for which only he has
the key. He then mails the box to person B. Person B cannot open the box, since he does
not have the key. Person B puts another padlock on the box for which only he has the
key. Person B then sends the box (with two padlocks on) back to person A. Person A
removes his padlock and sends the box back to person B. Person B removes his padlock,
opens the box, and removes the message.
If you want the same description the hard way, read through the following sections.