a second adder configured to {HEAD ~ modulo} add {TAIL ~ an output} of the fixed MD5 nonlinear function processing unit and the first adder 
add
a second adder configured to { HEAD ~ modulo } add { TAIL ~ an output } of the fixed MD5 nonlinear function processing unit and the first adder
OTH OTH OTH 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