ABSTRACT
Since cryptanalysis cannot exist without cryptography, this background chapter aims at making a brief, necessarily incomplete survey of modern cryptography, recalling some essential definitions and facts for the perusal of this book and laying down the notational ground. In particular, it presents various security notions, corresponding to several classes of adversaries. Modern cryptanalysis is the counterpart to these security notions. The fundamental goal of a cryptanalyst is to violate one or several of these security notions for algorithms that claim, implicitly or explicitly, to satisfy these security notions. This can be achieved in two main ways, either by overcoming an underlying security hypothesis or by exhibiting a specific flaw in the considered algorithm or protocol.
