Understanding and breaking the Caesar cipher
The caesar cipher is one the oldest known ciphers known to mankind. As the story goes, the Roman emperor Julius Caesar used it extensively for military communications. It is a simple substitution cipher and is not fit for any modern usage, since it is a trivial task to break it. However, it may be worthwhile to learn the roots of cryptography, as this cipher leads to more advanced ones like the Vigènere cipher and the unbreakable one-time pad cipher.