I did some work on this project several months ago, before deciding it wasn't viable. It turns out getting the code size small enough to fit on the CH554/CH552 is not a very easy task. Getting the thing to run crypto is therefore nearly impossible. 

I've tried working with some really really low footprint libraries for crypto; uECC (micro ECC) looked like a good bet. Even with space-optimized configuration, it didn't seem viable. I tried smaller libraries that I found on github (derivatives of uECC), and still found no luck. 

I don't think this project is viable, but it was fun exploring!