There are a number of interesting topics that are related to cryptography (Greek for secret writing), including classic cryptography. For example, in 400 BCE, the ancient Spartans were the first to employ a type of cryptography that used a scytale which was used to wrap a piece of parchment around it so that a message could be read but which was meaningless otherwise. Likewise, so-called Caesar ciphers which used letter substitutions were purportedly used by Julius Caesar used to conceal messages from adversaries. Another interesting topic about cryptography occurred during World War II when Allied cryptologists managed to capture an Enigma machine and key tables from the Nazis that allowed them to decode Axis messages as they were being transmitted.
More recently, computer-based cryptography technologies have emerged that have become far more difficult to crack, and cryptanalysis has become more sophisticated in response. Some other topics related to cryptography include public-key cryptography and cryptosystems.