History and technology of email encryption

Looking at a few of the oldest known ciphers, which demonstrate the fundamentals of encryption.

This post will focus on a columnar transposition cipher – a slightly more advanced transposition cipher that produces very different results.

The basic idea of a substitution cipher is a simple one: take one letter in your message, let’s say ‘A’, and replace it with a different letter, such as ‘E’. Sounds familiar?

The Vigenère cipher is a polyalphabetic substitution cipher and offers some defence against letter frequency analysis.