Subversion Repositories aes_pipe

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-- Project: AESFast

-- Author: Subhasis

-- Last Modified: 20/03/10

-- Email: subhasis256@gmail.com

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--

-- Description: The MixColumns operation

-- Ports:

--                      clk: System Clock

--                      in0: Byte 0 of a column

--                      in1: Byte 1 of a column

--                      in2: Byte 2 of a column

--                      in3: Byte 3 of a column

--                      out0: Byte 0 of output column

--                      out1: Byte 1 of output column

--                      out2: Byte 2 of output column

--                      out3: Byte 3 of output column

--                      keyblock: Input Key Blocks three at a time

--                      ciphertext: Output Cipher Block

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library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.std_logic_arith.all;

use IEEE.std_logic_unsigned.all;

library work;

use work.aes_pkg.all;

entity mixcol is

port(

        clk: in std_logic;

        in0: in std_logic_vector(7 downto 0);

        in1: in std_logic_vector(7 downto 0);

        in2: in std_logic_vector(7 downto 0);

        in3: in std_logic_vector(7 downto 0);

        out0: out std_logic_vector(7 downto 0);

        out1: out std_logic_vector(7 downto 0);

        out2: out std_logic_vector(7 downto 0);

        out3: out std_logic_vector(7 downto 0)

        );

end mixcol;

architecture rtl of mixcol is

signal d0, d1, d2, d3: std_logic_vector(7 downto 0);

signal t0, t1, t2, t3: std_logic_vector(7 downto 0);

signal sh0, sh1, sh2, sh3: std_logic_vector(7 downto 0);

signal xored: std_logic_vector(7 downto 0);

begin

        sh0(0) <= '0';

        sh1(0) <= '0';

        sh2(0) <= '0';

        sh3(0) <= '0';

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

        -- In GF(2^8) 2*x = (x << 1) xor 0x1b if x(7) = '1'

        --                  (x << 1) else

        -- This just left shifts each byte by 1.

        shift: for i in 7 downto 1 generate

                sh0(i) <= in0(i-1);

                sh1(i) <= in1(i-1);

                sh2(i) <= in2(i-1);

                sh3(i) <= in3(i-1);

        end generate;

        -- Conditional XOR'ing

        d0 <= sh0 xor X"1b" when in0(7) = '1' else

        sh0;

        d1 <= sh1 xor X"1b" when in1(7) = '1' else

        sh1;

        d2 <= sh2 xor X"1b" when in2(7) = '1' else

        sh2;

        d3 <= sh3 xor X"1b" when in3(7) = '1' else

        sh3;

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

        -- 3*x = 2*x xor x

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

        t0 <= d0 xor in0;

        t1 <= d1 xor in1;

        t2 <= d2 xor in2;

        t3 <= d3 xor in3;

        xored <= in0 xor in1 xor in2 xor in3;

        process(clk)

        begin

                if(rising_edge(clk)) then

                        out0 <= xored xor t0 xor d1;

                        out1 <= xored xor t1 xor d2;

                        out2 <= xored xor t2 xor d3;

                        out3 <= xored xor t3 xor d0;

                end if;

        end process;

end rtl;