Signing IPFS content with personal GPG/SSH Keypair

I’m interested in signing IPFS content with a personal keypair (not the Node’s keypair.) This seems pretty straight forward since we’re already addressing content by a hash. The advantage I see of not using the Node’s keypair is that anyone could author content using an identity through any IPFS node (or some type of proxy.)

This could be as simple as creating a signature from an IPFS hash with a private key (Alice) then encoding the signature in base58 or what have you. Alice could share the signature, alongside the hash, with Bob and Bob could verify with Alice’s public key.

I’m curious if this has been considered or if it has already been addressed in the spec.