FEP-1b12, “The Announce activity” section:
In case the incoming activity is deemed valid, the group MUST wrap it in an
Announceactivity, with the original activity as object. The wrapped activity MUST be preserved exactly as it was received, without changing or removing any properties. This ensures that forwarded activities can be verified with [Object Integrity Proofs].
How recipients of the Announce activity should verify the authenticity of the wrapped activity?
If wrapped activity contains an integrity proof, we can verify the proof and see that it was created by the actor. But, as far as I know, existing FEP-1b12 implementations don’t use integrity proofs. Do they re-fetch all wrapped activities from the server of origin?
This information seems to be missing from the FEP.