{TAIL ~ The strongest attack} known against {HEAD ~ HMAC} is the birthday attack, based on the frequency of collisions for the hash function 
{ TAIL ~ The strongest attack } known against { HEAD ~ HMAC } is the birthday attack , based on the frequency of collisions for the hash function
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH