[oflor]

I'm sorry, I don't have a good answer for you. While PGP-like web of trust is accessible on native desktop and mobile applications, it's certainly harder to use in browser. I don't think that it should be an argument against supporting it.

One of the widespread solutions in the cryptocurrency world is browser extensions, which store in its private storage the private key and allow you to use it to sign some transactions in the same browser window. I reckon it's possible to implement the same approach for PGP and store the private key and trusted public keys in order to sign and validate messages.