Thanks for the advice, unfortunately I won’t be eligible next year but I hope someone who is will see this and start preparing now :).
I had made programs to break ciphers automatically using methods I researched online, and it was very satisfying to be able to put in an encrypted vigenere or simple substitution cipher into my program, and it would return a decrypted output in a reasonable amount of time and submitting answers minutes after release this year.
I will have a look at the cryptopals challenges, they look interesting and will be good to learn about modern cryptography.
If I have the time, I hope to keep doing the cipher challenge for fun over the next few years too.
Your cryptography guide is amazing btw 🙂