The History of Encryption

The Caesar Cipher

A substitution cipher. Either you can shift to the right or to left by any number of spaces you like.

ROT 13

Single alphabet substitution cipher.

Multi-Alphabet Substitution

In this scheme, you select multiple numbers by which to shift letters (that is, multiple substitution alphabets).

Rail Fence

A type of transposition cipher.

A      tc      a      dw

      ta      k      ta      n

Becomes: atcadwtaktan

Vigenère

Vigenère is a polyalphabetic cipher and uses multiple substitutions in order to disrupt letter and word frequency.

Enigma

The Enigma is a sort of mechanical polyalphabetic cipher. The operator of the Enigma machine would be given a message in plaintext and then type that message into Enigma. For each letter that was typed in, Enigma would provide a different ciphertext based on a different substitution alphabet. The recipient would type in the ciphertext, getting out the plaintext, provided both Enigma machines had the same rotor settings.