This book consolidates several key aspects from the state-of-the-art research in symmetric key cryptography, which is among the cornerstones of digital security. It presents the content in an informative yet beginner-friendly, accompanied with toy examples and comprehensible graphics. In particular, it highlights the recent developments in tool-assisted analysis of ciphers. Furthermore, promising device-dependent attacks, such as fault attack and side channel attacks on symmetric key ciphers, are discussed in detail. One salient feature of this book is to present a detailed analysis of various fault countermeasures. The coverage of our book is quite diverse--it ranges from prerequisite information, latest research contribution as well as future research directions. It caters to students and researchers working in the field of cryptography.