Chapter 9 – Public Key Algorithms

This chapter introduces the concept of public key cryptography. Public key algorithms, also known as asymmetric key algorithms, are used to solve two problems that cannot be solved by symmetric key algorithms: key distribution and nonrepudiation. The first helps solve privacy problems, and the latter helps solve authenticity problems. Public key algorithms accomplish these goals by operating asymmetrically; that is, a key is split into two corresponding parts, a public key and a private key. The public key is so named as it is secure to give out publicly to all those who ask for it. The public key enables people to encrypt messages and verify signatures. The private key is typically owned by a single person or device in most circumstances, but could technically be shared among a trusted set of parties. The private key allows for decrypting messages and the generation of signatures. The chapter also discusses two public key algorithms. First, the Rivest Shamir Adleman (RSA) algorithm and its related Public Key Cryptographic Standards #1 (PKCS # 1) padding scheme are presented along with various timing attacks and their respective counter-measures. Next, the chapter presents the Elliptic Curve Cryptography (ECC) public key algorithms Elliptic Curve Diffie–Hellman (EC-DH) and Elliptic Curve-Digital Signature Algorithm (EC-DSA).