{TAIL ~ An attacker} must instead search for {HEAD ~ a collision message} that hashes to the same value  
{ TAIL ~ An attacker } must instead search for { HEAD ~ a collision message } that hashes to the same value
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH