On how (not) to break crypto systems

In this overview talk we focus on the question "What is a secure encryption scheme?". We shall start with a discussion of classical encryption schemes, and see why they are insecure. Based on these examples we develop an intuitive notion of secure encryption. We then formalize this intuition and discuss the notion of "IND-CPA security", which is a widely accepted definition for "secure encryption" in the crypto community. We shall see that - under certain assumptions - AES based symmetric encryption schemes can be mathematically proved to be IND-CPA secure. Finally, we discuss what these rather theoretical security considerations mean in practice. In the course of this discussion, we give an overview of side channel attacks, such as, timing and power analysis attacks.