Here is a challenge by AIVD (General Intelligence and Security Service of the Netherlands):
https://www.aivd.nl/organisatie/eenheden/nationaal-bureau/nieuws/aivd-cyber-challenge/

I won't say anything else because I think it's not fair, but I encourage you to give it a try! It's a nice challenge btw, and I would like to see much more like this one! And yes, it's possible to decrypt the ENCrypted file

Have phun!