Right, but that's likely multiple days of dev work. MediaGoblin's source code is a bit of a mess, and it's not GCS-aware at all, so it's non-trivial to implement support for GCS signed URLs and secure key management.

What would be the value? If my family members send a link to someone else, that person will have the link forever? If the unauthorized person has a link to a video, they can simply download that video and keep it forever anyway. They can't retrieve other videos in the bucket unless they can correctly guess their (not very predictable) filenames.