source 2001 Bernstein "A software implementation of NIST P-224"
appliesto jacobian-3
compute delta = Z1^2
compute gamma = Y1^2
compute beta = X1 gamma
compute alpha = 3 (X1-delta) (X1+delta)
compute X3 = alpha^2-8 beta
compute Z3 = (Y1+Z1)^2-gamma-delta
compute Y3 = alpha (4 beta-X3)-8 gamma^2