Technically, cryptocurrencies aren't illegal, as long as you don't use it for criminal activity. If you sign up with an exchange, and that they get a tip from law enforcement, they have the right to freeze your assets.
@SylverReZ, speaking of crypto i remember reading about a guy who spend like 10 grand bitcoin on a couple pizzas (when bitcoin wasnt as worthy as nowadays)
@SylverReZ, I also recall watching a video of some failed games with their own crypto currency or smth like that, lemme link it to you (it's in spanish tho)