Introduction to ciphers and substitution. Alice and Bob and Carl and Julius: terminology and Caesar Cipher ; The key to the matter: generalizing the Caesar Cipher ; Multiplicative ciphers ; Affine ...

Introduction If you need to send a secret message to a friend, how could you prevent other people from reading it? One way is to encrypt the message—that is, use a secret code that only you and your ...

Introduction The Shorter Oxford English Dictionary lists the 5th meaning of the word cipher as, “A secret manner of writing by any of various methods, intelligible only to those possessing the key ...