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-- ------------------------------------------------------------------------

-- Copyright (C) 2005 Arif Endro Nugroho

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-- 

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-- ------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

use work.xtime_pkg.all;

entity mix_column is

  port (

    s0          : in  std_logic_vector (07 downto 00);

    s1          : in  std_logic_vector (07 downto 00);

    s2          : in  std_logic_vector (07 downto 00);

    s3          : in  std_logic_vector (07 downto 00);

    mix_col     : out std_logic_vector (31 downto 00);

    inv_mix_col : out std_logic_vector (31 downto 00)

    );

end mix_column;

architecture data_flow of mix_column is

  type state is array (03 downto 00) of std_logic_vector (07 downto 00);

  signal mc : state :=

    ( X"00", X"00", X"00", X"00" );

begin

  --

  -- MixColumn   : a(x)  = {03}x^3 + {01}x^2 + {01}x + {02}

  --

  -- s'0c = | 02 03 01 01 | s0c

  -- s'1c = | 01 02 03 01 | s1c

  -- s'2c = | 01 01 02 03 | s2c

  -- s'3c = | 03 01 01 02 | s3c

  --

  -- InvMixColumn: a'(x) = {0B}x^3 + {0D}x^2 + {09}x + {0E}

  --               a'(x) = {03}x^3 + {01}x^2 + {01}x + {02} +

  --                       {08}x^3 + {08}x^2 + {08}x + {08} +

  --                                 {04}x^2 + {04}x

  --  a(x) * a'(x)     = {01}

  --  a(x) * {a'(x)}^2 = {01} * a'(x) = a'(x)

  --         {a'(x)}^2 = {04}x^2 + {05}

  --

  --              | 05 00 04 00 |          | 0E 0B 0D 09 |   E = 14 = 1110 = 8 xor 4 xor 2 = 1000 xor 0100 xor 0010

  --  {a'(x)}^2 = | 00 05 00 04 |  a'(x) = | 09 0E 0B 0D |   D = 13 = 1101 = 8 xor 4 xor 1 = 1000 xor 0100 xor 0001

  --              | 04 00 05 00 |          | 0D 09 0E 0B |   B = 11 = 1011 = 8 xor 2 xor 1 = 1000 xor 0010 xor 0001

  --              | 00 04 00 05 |          | 0B 0D 09 0E |   9 = 09 = 1001 = 8 xor 0 xor 1 = 1000 xor 0000 xor 0001

  --

  mc (3) <= xtime_2(s0) xor xtime_2(s1) xor s1 xor s2 xor s3;

  mc (2) <= s0 xor xtime_2(s1) xor xtime_2(s2) xor s2 xor s3;

  mc (1) <= s0 xor s1 xor xtime_2(s2) xor xtime_2(s3) xor s3;

  mc (0) <= xtime_2(s0) xor s0 xor s1 xor s2 xor xtime_2(s3);

--

  mix_col <= (mc(3) & mc(2) & mc(1) & mc(0));

-- 

  inv_mix_col (31 downto 24) <= xtime_4(mc(3)) xor mc(3) xor xtime_4(mc(1));

  inv_mix_col (23 downto 16) <= xtime_4(mc(2)) xor mc(2) xor xtime_4(mc(0));

  inv_mix_col (15 downto 08) <= xtime_4(mc(1)) xor mc(1) xor xtime_4(mc(3));

  inv_mix_col (07 downto 00) <= xtime_4(mc(0)) xor mc(0) xor xtime_4(mc(2));

--

--   inv_mix_col (31 downto 24) <= 

--                                 xtime_8(mc(3)) xor xtime_4(mc(3)) xor xtime_2(mc(3)) xor 

--                                 xtime_8(mc(2)) xor xtime_2(mc(2)) xor mc(2) xor

--                                 xtime_8(mc(1)) xor xtime_4(mc(1)) xor mc(1) xor

--                                 xtime_8(mc(0)) xor mc(0);

--   inv_mix_col (23 downto 16) <= 

--                                 xtime_8(mc(3)) xor mc(3) xor

--                                 xtime_8(mc(2)) xor xtime_4(mc(2)) xor xtime_2(mc(2)) xor 

--                                 xtime_8(mc(1)) xor xtime_2(mc(1)) xor mc(1) xor

--                                 xtime_8(mc(0)) xor xtime_4(mc(0)) xor mc(0);

--   inv_mix_col (15 downto 08) <= 

--                                 xtime_8(mc(3)) xor xtime_4(mc(3)) xor mc(3) xor

--                                 xtime_8(mc(2)) xor mc(2) xor

--                                 xtime_8(mc(1)) xor xtime_4(mc(1)) xor xtime_2(mc(1)) xor 

--                                 xtime_8(mc(0)) xor xtime_2(mc(0)) xor mc(0);

--   inv_mix_col (07 downto 00) <= 

--                                 xtime_8(mc(3)) xor xtime_2(mc(3)) xor mc(3) xor

--                                 xtime_8(mc(2)) xor xtime_4(mc(2)) xor mc(2) xor

--                                 xtime_8(mc(1)) xor mc(1) xor

--                                 xtime_8(mc(0)) xor xtime_4(mc(0)) xor xtime_2(mc(0));

end data_flow;