It's been a while since I've used stripe but don't their keys start with sk_ for secret and pk_ for public?

I like that. Easy to tell if you should keep the key a secret or not.

They do, yeah.

(Although `pk` always freaks me out. Public or private?! Oh, right, the other one's "secret".)

Or is `sk` shared key and `pk` private key...

Honestly we should just always call them public and secret key to avoid confusion