source 2007 Hisil--Carter--Dawson
parameter b
assume b = a - 1
compute E = S1^2
compute F = C1^2
compute G = E^2
compute H = F^2
compute J = 2 H
compute K = 2 J
compute L = (2 F+E)^2-G-K
compute M = b G
compute N = K+J
compute P = M^2
compute R = N M
compute U = M L
compute V = H^2
compute W = H L
compute S3 = S1(R+b W+2(P-V)-W-P-V)
compute C3 = C1(2(P-V)-U+P+V-R+b U)
compute D3 = D1(U-P-V+R+b W)
compute Z3 = Z1(R-b U-W-P-V)