source 2001 Joye--Quisquater "Hessian elliptic curves and side-channel attacks" compute T1 = X1 compute T2 = Y1 compute T3 = Z1 compute T4 = X2 compute T5 = Y2 compute T6 = Z2 compute T7 = T1 T6 compute T1 = T1 T5 compute T5 = T3 T5 compute T3 = T3 T4 compute T4 = T2 T4 compute T2 = T2 T6 compute T6 = T2 T7 compute T2 = T2 T4 compute T4 = T3 T4 compute T3 = T3 T5 compute T5 = T1 T5 compute T1 = T1 T7 compute T1 = T1-T4 compute T2 = T2-T5 compute T3 = T3-T6 compute X3 = T2 compute Y3 = T1 compute Z3 = T3