The book focuses against the current static approach taken to arrive at a solution on these security issues. In doing so it addresses the security issue in pervasive computing with the based on context based approach. In a pervasive scenario the interaction levels and the resources available are variable depending on the context. The new approach to the security policies would give more flexibility in the security actions taken, depending on the resources in the computing environment. The book advocates such a context based approach investigating the modelling of context in security policies in the three formalisms-mobile ambients (with “ambient” as context), rule based reasoning (with context as rule conditions), and contextual graphs. The book also exploits the notion of ambient calculus for the range of security actions, which makes it different from many other existing security policies. The book firsts builds a multi level security model based on the ambient concepts. This model provides a controlled approach towards accessing valuable resources. The book then uses this model to achieve the goal of modelling context based security policies in a pervasive computing environment.