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 ...

In general, you want to avoid writing down sensitive information and just keeping it in your head but that's not always an option. If you have to write down a password, or some other sensitive ...

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 ...