The layers may be encrypted using {HEAD ~ a separate key} for {TAIL ~ each layer}, and rights to a key granted by permission 
for
The layers may be encrypted using { HEAD ~ a separate key } for { TAIL ~ each layer } , and rights to a key granted by permission
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH