Textbook in PDF format Security and science are the building blocks of the modern civilization. Science gave us the powers to change the world. Security should protect us from abuses of those powers. Yet humans have been hesitant to apply the methods of science to the problems of security. This core security-science (SecSci) textbook is a step in that direction. While many students pursue security out of genuine interest, most security curricula are plastered with industry buzzwords and policy slogans, driven by market incentives and government funding. The result is the attackers get richer, and their victims get poorer—while security experts inhabit the realm of informal narratives in-between. Before joining the fray, some students want to understand it. This textbook arose from the authors' efforts to cater to such students by peeling off the veils of expertise and replacing them with explanations and simple mathematical models