When you say crypto do you mean cryptography or cryptocurrencies?

As of today, I'm not sure focusing exclusively on cryptocurrencies will give you much knowledge in security... the majority of the day-to-day security work I've seen related to cryptocurrencies is detecting and turning down crypto miners.

If you're interested in security, I'd personally start with either web/application security, or infrastructure by picking your favorite cloud (AWS, Google, Azure, ...) and learn their security offerings.