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.