This is course extends the broad overview of information security presented in INTE1120 Introduction to Information Security and INTE1122 Case Studies in Information Security. It will provide you with a detailed understanding of information theoretic techniques which underpin the design of information security systems. Topics covered in this course include confusion, diffusion, entropy, unicity distance, guessing entropy, perfect secrecy, correlation attacks and probabilistic approximations of nonlinear functions. You are also introduced to the fundamental concepts in information theory including conditional entropies and Shannon and Renyi entropies and their use in characterizing the security of secrecy systems.