An increased interest in stream ciphers has recently been reflected in a number of applications for securing environments with constrained resources in computing power and energy as well as areas where very high speed is required in software implementations. This book covers the field of symmetric cryptography and provides a basic understanding of stream ciphers and pseudo-random sequences for system design and implementation purposes. The authors discuss key stream ciphers, e-stream competition, applications of stream ciphers, cryptanalysis, and various types of attacks.