A major concern in today's digital world is Security. Due to digitization, implementation of secure policies and procedures to ensure security became challenging issue. Also analyzing the strength of security algorithms or procedures is more important to avoid compromising of organizational assets. In this direction, this book explains the role of cryptanalysis in real world with practical examples. Cryptanalysis of various algorithms by using emerging technologies is explained which is helpful for reader/learner to implement innovative cryptanalysis schemes that assists to evaluate the existing cryptographic algorithms. This book also demonstrated different ways of evaluating the security of the system in the form of penetration testing. Tools for performing penetration testing is well illustrated with stepwise procedure which will give hands-on experience to the reader/audience. The role of data mining schemes in the context of intrusion detection system (IDS) is also illustrated. This book enlighten the use of IoT based security application in solving the social issues. Such demonstrated applications in this book will help readers/audiences to implement their own novel applications for addressing different societal issues. We consider all aforementioned features as the strength of this book. With this impression we ensures that all undergraduate and postgraduate students of any discipline will get a basic idea on cryptography, cryptanalysis, penetration testing tools, cyber security, IDS and IoT applications in securing today's digitalized world.