These two ciphers are simple enough: they require only that letters are substituted with others in the alphabet. The Caesar cipher involves shifting each letter of a text a fixed number of places along the alphabet. The Vigenère cipher adds another layer of complexity by employing a keyword to unlock encryption.
The Caesar Shift
Named after Julius Caesar, the Caesar cipher is an extremely simple, and insecure, form of encryption. It is said that Caesar used a shift of three letters to encode his personal communication, so we’ll take that as an example here.
Applying a shift of three to a text results in every letter moving three places along the alphabet; so an A becomes a D, a B becomes an E and so on. In this way, the message ‘The party will be on November ninth’ would be encoded as ‘Wkh sduwb zloo eh rq qryhpehu qlqwk’.