4.6 Summary
In this chapter, we covered a lot of ground. With the goal of confidentiality in mind, we have formally defined symmetric cryptosystems and have seen that perfectly secure cryptosystems do exist. Inspired by the prime example of a perfectly secure cipher, the one-time pad, we looked for less expensive ways to achieve a desired level of security. This led us to weaken the concepts of perfect security and true randomness and to look at computational security and pseudorandomness instead. These concepts will be important tools in what’s to follow.
In the next chapter, we will look at another important security objective from the CIA triad, namely authentication.
