January 2018
Intermediate to advanced
416 pages
10h 40m
English
“The encryption genie is out of the bottle.”—Jan Koum, WhatsApp founder

Before we start writing cipher programs, let’s look at the process of encrypting and decrypting with just pencil and paper. This will help you understand how ciphers work and the math that goes into producing their secret messages. In this chapter, you’ll learn what we mean by cryptography and how codes are different from ciphers. Then you’ll use a simple cipher called the Caesar cipher to encrypt and decrypt messages using paper and pencil.