to sign events, see https://atproto.com/specs/cryptography
they support either secp256k1 or secp256r1 (which i found kind of a weird choice, just choose one ffs) 

 I assumed it was ed255519 

 OK, the how makes sense. Still bugged by "why secp and not ed25519"  

 their rationale seems to be TPMs and HSMs, though id assume a lot support ed25519 as well due to ssh