Serious Cryptography, 2nd Edition

1 ENCRYPTION

Encryption is the principal application of cryptography; it makes data incomprehensible to ensure its confidentiality. Encryption uses an algorithm called a cipher and a secret value called the key. If you don’t know the secret key, you can’t decrypt, nor can you learn any bit of information on the encrypted message—and neither can any attacker.

This chapter focuses on symmetric encryption, which is the simplest kind of encryption. In symmetric encryption, the decryption key is the same as the encryption key (unlike asymmetric encryption, or public-key encryption, in which the keys are different). You’ll start by learning about ...