Code Breaking

Background

In classic cryptography there are two primary types of ciphers: substitution ciphers and transposition ciphers.

Substitution ciphers change, or substitute, characters within the message while transposition ciphers rearrange the characters in a message.

For example, a caesar cipher is a substitution cipher while reversing a message is a type of transposition cipher.

Given a sufficiently long encrypted text, we can determine whether the text was encrypted via a substitution or transposition cipher by using frequency analysis.