source 2007 Hisil--Carter--Dawson
parameter b
assume b = a - 1
compute R0  =  S1^2
compute R1  =  C1^2
compute R2  =  R0^2
compute R3  =  R1^2
compute R4  =  2 R3
compute R5  =  2 R4
compute R6  =  2 R1
compute R6  =  R6+R0
compute R6  =  R6^2
compute R6  =  R6-R2
compute R6  =  R6-R5
compute R2  =  b R2
compute R5  =  R5+R4
compute R4  =  R2^2
compute R0  =  R5 R2
compute R5  =  R2 R6
compute R2  =  R3^2
compute R1  =  R3 R6
compute R3  =  R4-R2
compute R2  =  R4+R2
compute R4  =  2 R3
compute R3  =  b R1
compute R6  =  b R5
compute R3  =  R0+R3
compute R1  =  R1+R2
compute R0  =  R0-R6
compute R2  =  R5-R2
compute R5  =  R3+R4
compute R5  =  R5-R1
compute S3  =  S1 R5
compute R4  =  R4-R2
compute R4  =  R4-R0
compute C3  =  C1 R4
compute R2  =  R2+R3
compute D3  =  D1 R2
compute R0  =  R0-R1
compute Z3  =  Z1 R0