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-- Copyright: 2010 Integrated Sytems Laboratory, ETH Zurich
--            http://www.iis.ee.ethz.ch/~sha3
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library ieee;
use ieee.numeric_std.all;
use ieee.std_logic_1164.all;

entity permix is

  port (
    MxDI         : in  std_logic_vector(255 downto 0);
    PerselectxSI : in  std_logic;
    CntxDI       : in  unsigned(2 downto 0);
    MxDO         : out std_logic_vector(255 downto 0));

end permix;

architecture rtl of permix is

  signal P0xD : unsigned(63 downto 0);
  signal P1xD : unsigned(63 downto 0);
  signal P2xD : unsigned(63 downto 0);
  signal P3xD : unsigned(63 downto 0);

  signal Pa0xD : unsigned(63 downto 0);
  signal Pa1xD : unsigned(63 downto 0);
  signal Pa2xD : unsigned(63 downto 0);
  signal Pa3xD : unsigned(63 downto 0);

  signal Pb0xD : unsigned(63 downto 0);
  signal Pb1xD : unsigned(63 downto 0);
  signal Pb2xD : unsigned(63 downto 0);
  signal Pb3xD : unsigned(63 downto 0);

  signal Pc0xD : unsigned(63 downto 0);
  signal Pc1xD : unsigned(63 downto 0);
  signal Pc2xD : unsigned(63 downto 0);
  signal Pc3xD : unsigned(63 downto 0);

  signal Pd0xD : unsigned(63 downto 0);
  signal Pd1xD : unsigned(63 downto 0);
  signal Pd2xD : unsigned(63 downto 0);
  signal Pd3xD : unsigned(63 downto 0);

  signal RotationxS : integer;
  
  signal Rotation1axS : integer;
  signal Rotation1bxS : integer;
  signal Rotation2axS : integer;
  signal Rotation2bxS : integer;
  signal Rotation3axS : integer;
  signal Rotation3bxS : integer;
  signal Rotation4axS : integer;
  signal Rotation4bxS : integer;

  type integerx8 is array (0 to 7) of integer;

  constant rotconst0 : integerx8 := (26, 20, 53, 35, 11, 42, 59, 50);
  constant rotconst1 : integerx8 := ( 5, 56, 36, 28, 13, 46, 58, 44);
                                                             
  
begin  -- rtl

  RotationxS <= rotconst1(to_integer(CntxDI)) when PerselectxSI = '1' else
                rotconst0(to_integer(CntxDI));

  P0xD <= unsigned(MxDI(255 downto 192)) when CntxDI(0) = '0' else
          unsigned(MxDI(127 downto 64));
  
  P1xD <= unsigned(MxDI(191 downto 128)) when (CntxDI(1) xor CntxDI(0)) = '0' else
          unsigned(MxDI(63 downto 0));

  P2xD <= P0xD + P1xD;
  P3xD <= (P1xD rol RotationxS) xor P2xD;

  MxDO(255 downto 192) <= std_logic_vector(P2xD) when CntxDI(0) = '0'                 else MxDI(255 downto 192);
  MxDO(191 downto 128) <= std_logic_vector(P3xD) when (CntxDI(1) xor CntxDI(0)) = '0' else MxDI(191 downto 128);
  MxDO(127 downto 64)  <= std_logic_vector(P2xD) when CntxDI(0) = '1'                 else MxDI(127 downto 64);
  MxDO(63 downto 0)    <= std_logic_vector(P3xD) when (CntxDI(1) xor CntxDI(0)) = '1' else MxDI(63 downto 0);
  
--  Rotation1axS when PerselectxSI = '1' else 26;
--  Rotation1bxS when PerselectxSI = '1' else 20;
--  Rotation2axS when PerselectxSI = '1' else 53;
--  Rotation2bxS when PerselectxSI = '1' else 35;
--  Rotation3axS when PerselectxSI = '1' else 11;
--  Rotation3bxS when PerselectxSI = '1' else 42;
--  Rotation4axS when PerselectxSI = '1' else 59;
--  Rotation4bxS when PerselectxSI = '1' else 50;

--  P0xD MxDI(255 downto 192));
--  P1xD MxDI(191 downto 128));
--  P2xD MxDI(127 downto 64));
--  P3xD MxDI(63 downto 0));

--  Pa0xD P0xD + P1xD;
--  Pa3xD P1xD rol Rotation1axS) xor Pa0xD;
--  Pa2xD P2xD + P3xD;
--  Pa1xD P3xD rol Rotation1bxS) xor Pa2xD;

--  Pb0xD Pa0xD + Pa1xD;
--  Pb3xD Pa1xD rol Rotation2axS) xor Pb0xD;
--  Pb2xD Pa2xD + Pa3xD;
--  Pb1xD Pa3xD rol Rotation2bxS) xor Pb2xD;

--  Pc0xD Pb0xD + Pb1xD;
--  Pc3xD Pb1xD rol Rotation3axS) xor Pc0xD;
--  Pc2xD Pb2xD + Pb3xD;
--  Pc1xD Pb3xD rol Rotation3bxS) xor Pc2xD;

--  Pd0xD Pc0xD + Pc1xD;
--  Pd3xD Pc1xD rol Rotation4axS) xor Pd0xD;
--  Pd2xD Pc2xD + Pc3xD;
--  Pd1xD Pc3xD rol Rotation4bxS) xor Pd2xD;

--  MxDO(255 downto 192) Pd0xD);
--  MxDO(191 downto 128) Pd1xD);
--  MxDO(127 downto 64)  Pd2xD);
--  MxDO(63 downto 0)    Pd3xD);

end rtl;