nostr:npub1xaklulvyjhcvljrd4lgn7cswj5sa9ewphvn0zswq0gfcadn2qv0qlwudwf If reference to media file is did:apkey URL, it can be translated similarly to object IDs.

Instead of encoding content hash directly in the URL, one can specify it in the object that represents media attachment:

{
  "type": "Image",
  "mediaType": "image/jpeg",
  "href": "did:apkey:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK/media/1.jpg?hosts=server1.example,server2.example",
  "digestHex": "deadbeef"
}