“I should be able to whisper something in your ear, even if your ear is 1000 miles away, and the government disagrees with that.”—Philip Zimmermann, creator of Pretty Good Privacy (PGP), the most widely used email encryption software in the world


In Chapter 13, you learned that the affine cipher is actually the multiplicative cipher combined with the Caesar cipher (Chapter 5), and the multiplicative cipher is similar to the Caesar cipher except it uses multiplication instead of addition to encrypt messages. In this chapter, you’ll build and run programs to implement the affine cipher. Because the affine cipher uses ...

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