The origins of linear cryptanalysis can be traced back to a number of seminal works of the early 1990s. Since its invention, several theoretical and practical aspects of the technique have been studied, understood and generalized, resulting in more elaborated attacks against certain ciphers, but also in some negative results regarding the potential of various attempts at generalization. This book gives an overview of the current state of the discipline and it takes a look at potential future developments, and is divided into five parts. The first part deals with basic assumptions in linear cry.