When cryptopals is mentioned, i've also gotta mention "Cryptohack": https://cryptohack.org/ https://cryptohack.org/ That's where i've learnt most of my crypto,

When cryptopals is mentioned, i've also gotta mention "Cryptohack": https://cryptohack.org/ https://cryptohack.org/ That's where i've learnt most of my crypto, although it might be more focussed on the breaking than the making part.