ABSTRACT
Recall that a public-key cryptosystem is a cryptosystem with two distinct, but related keys. Each user of the cryptosystem has a public key, which he or she makes public, so that anyone else can use it to encrypt messages to the user. The user also has a private key, known to nobody else, which is used for decryption. To make the system secure, it is important that there is no easy way to determine a private key from the corresponding public key. To do this requires some nifty mathematics, as we shall see.
