Foundations of Symmetric Cryptography

This chapter presents theoretical foundations of symmetric-key cryptography, or secret-key cryptography. The currently most widely used symmetric algorithms are given. It starts with the concept of a Feistel network which constitutes an important design principle underlying many advanced symmetric encryption schemes. Among the most well-known symmetric-key ciphers are DES (Data Encryption Standard) and its official successor AES (Advanced Encryption Standard), followed by several others also well known and also often used in practice such as IDEA (International Data Encryption Algorithm) or the RC (Rivest Cipher) family of algorithms.