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