source 2001 Bernstein http://cr.yp.to/nistp224.html opt-idea53.c ecadd
unified
compute ZZ1 = Z1^2
compute ZZZ1 = Z1 ZZ1
compute ZZ2 = Z2^2
compute ZZZ2 = Z2 ZZ2
compute A = X1 ZZ2
compute B = X2 ZZ1 -A
compute c = Y1 ZZZ2
compute d = Y2 ZZZ1 -c
compute e = B^2
compute f = B e
compute g = A e
compute h = Z1 Z2
compute f2g = 2 g+f
compute X3 = d^2-f2g
compute Z3 = B h
compute gx = g-X3
compute Y3 = d gx-c f
