applying to each of the segments a threshold encryption scheme using {HEAD ~ a first key} from {TAIL ~ the first set} of keys and a second key from the second set of keys 
from
applying to each of the segments a threshold encryption scheme using { HEAD ~ a first key } from { TAIL ~ the first set } of keys and a second key from the second set of keys
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH