Wouldn't it make sense to use GPG as the activitypub user?
I was thinking about this while trying to use Mastadon. I don't get why I have to create an account on every Mastadon server just to read. The thing is that GPG is already a federated "user identification" system so why not use that to sign posts. And with Mastadon doing the ActivityPub thing I think GPG should spread to ActivityPub too. Think about it, this is what GPG was designed for.
👤 nl Accepted Answer ✓
The W3C DID spec enables private-key based identity in a generic way. It grew out of the ideas behind KeyBase.
There's a bunch of different DID methods, some of which use crypto ledgers to enable public key distribution. If that isn't what you want, the DID:key method[1] might be interesting.