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, ...

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 could do worse than to confuse the meanings of "code" and "cipher"—even cryptographers sometime use the terms as though they had the same meaning. There is, however, a definite distinction between ...