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 ...

You can make a message secret in countless different ways. One common way is to use a substitution cipher, in which one letter is substituted for another. Another is to employ a transposition cipher, ...

Here's your chance to crack ciphers similar to those Bletchley Park's codebreakers faced during World War II. Below, we present three ciphers of different levels of difficulty, from easiest to most ...