The first chapter provides a thorough treatment of the mathematics necessary to understand cryptography, including number theory and complexity, while the second chapter discusses the basics of cryptography, such as ciphers, linear feedback shift registers, modes of operation, and attack. The book concludes with an attachment on mathematical data, computer arithmetic, Rijndael S-Box, knapsack ciphers, algorithm, Silver-Pohlig-Hellman, SHA-1 algorithm, radix-64 encoding, and quantum cryptography. New Second Edition: An introductory chapter that provides more information about the facts of mathematics and complexity theory Expanded and updated exercises sets, including some routine exercises More information on primality testing and cryptanalysis Accessible and logical, An Introduction to Cryptography, Second Edition is an important book about the basics of cryptography.