Need help deciding between Cryptography and Games Design

Although this is more-so a question on University courses, given it governs my larger career, I wanted to ask here.

I love Cryptography as a subject; I study it in my free time, it's really engaging, the math is really fun. I love it!! But the problem is, I love Games Design more. I love making games, implementing mechanics, seeing playtests and adjusting. It's just an unbelievable high that I can't get rid of.

I'd be fine doing Cryptography as a career, but I'd be ecstatic to do Games Design (And level design particularly!). I'm at the stage in my school where if I want to do Games Design, I should start preparing a portfolio. I wanted to ask; Could you guys weigh in on what you think I should choose?

I appreciate that this is my choice and my choice only, but I'm concerned because I don't have a firm opinion on this yet, and want to try and make a more assured choice. Games Design would be the more enjoyable career, but it would certainly be a more tumultuous one - Many people competing for few jobs with lower pay, its just really risky. So I'm not sure whether to go with Games Design, or be safer and choose Cryptography!

Another thing; I could also choose Games Development. Where Games Design is the discipline of coming up with levels/mechanics (And sometimes scripting them), Games Development is the discipline of making the engine and code behind games. This is something I KNOW I could get into very safely, given I take Maths, Further Maths, and Computer Science (And it lets me apply to other Universities with more general Comp Sci degrees!!) but I'd probably be the most miserable doing it.

So I'm not sure where to go! Any advice would be greatly appreciated. I love both subjects dearly, and want to do Game Design as a passion, but I've also got to be realistic about the industry I'm entering. How do you decide in these moments?