We began the course with a discussion and review of private key cryptography and then started moving into the realm of public key cryptography. During this lecture, we will discuss four public key schemes. Even though RSA preceded the other schemes presented here, we will review ElGamal and introduce DSS rst (both mod p schemes), in hopes of providing more background and motivation for some of the concepts utilized in RSA. Finally, we will also provide a brief introduction to the theory of Elliptic Curves. Throughout this lecture, we will primarily consider public key cryptography as it relates to digital signatures.