Install tails documentation: not need more an intermediary key
In this page:
if you click Download Tails (Torrent file).. the next step is:
1.3 Continue installing
Open and download the Torrent file with your BitTorrent client. It contains the Tails 3.12 USB image that you will use in the next step.
“install an Intermediary key”
but is the final key.