@Shinglington, good. Nice to hear that someone is learning something. If you want to win next year (if you are eligible),
then the time to start preparing is now. Not just encryptors and decryptors: you will need to build programs that
break ciphers for you.
All of the past ciphertexts are in this archive, even when the official sites are down:
You can use them as practice as you build your crackers. Also, try to think of ways Harry can tweak a cipher, and
see if you can still break it.
If you have interest in modern cryptography, the cryptopals tasks are a good way to learn while you hone your
programming skills. They explain everything rather well (until sets 7 and 8). Harry censors web links, so you have to search for it.