-- ======================================================================
-- CBC-MAC-AES
-- Copyright (C) 2020 Torsten Meissner
-------------------------------------------------------------------------
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 2 of the License, or
-- (at your option) any later version.

-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-- GNU General Public License for more details.

-- You should have received a copy of the GNU General Public License
-- along with this program; if not, write to the Free Software
-- Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
-- ======================================================================


library ieee;
  use ieee.std_logic_1164.all;
  use ieee.numeric_std.all;

use work.aes_pkg.all;



entity cbcmac_aes is
  port (
    reset_i     : in  std_logic;                   -- low active async reset
    clk_i       : in  std_logic;                   -- clock
    start_i     : in  std_logic;                   -- start cbc
    key_i       : in  std_logic_vector(0 to 127);  -- key input
    data_i      : in  std_logic_vector(0 to 127);  -- data input
    valid_i     : in  std_logic;                   -- input key/data valid flag
    accept_o    : out std_logic;                   -- input accept
    data_o      : out std_logic_vector(0 tO 127);  -- data output
    valid_o     : out std_logic;                   -- output data valid flag
    accept_i    : in  std_logic                    -- output accept
  );
end entity cbcmac_aes;



architecture rtl of cbcmac_aes is


  -- CBCMAC must have fix IV for security reasons
  constant C_IV : std_logic_vector(0 to 127) := (others => '0');

  signal s_aes_datain    : std_logic_vector(0 to 127);
  signal s_aes_dataout   : std_logic_vector(0 to 127);
  signal s_aes_dataout_d : std_logic_vector(0 to 127);
  signal s_aes_key       : std_logic_vector(0 to 127);
  signal s_key           : std_logic_vector(0 to 127);
  signal s_aes_accept    : std_logic;
  signal s_aes_validout  : std_logic;


begin


  s_aes_datain <= C_IV xor data_i when start_i = '1' else
                  s_aes_dataout_d xor data_i;

  data_o <= s_aes_dataout;

  s_aes_key <= key_i when start_i = '1' else s_key;

  accept_o <= s_aes_accept;

  valid_o <= s_aes_validout;


  inputregister : process (clk_i, reset_i) is
  begin
    if (reset_i = '0') then
      s_key <= (others => '0');
    elsif (rising_edge(clk_i)) then
      if (valid_i = '1' and s_aes_accept = '1' and start_i = '1') then
        s_key <= key_i;
      end if;
    end if;
  end process inputregister;


  outputregister : process (clk_i, reset_i) is
  begin
    if (reset_i = '0') then
      s_aes_dataout_d <= (others => '0');
    elsif (rising_edge(clk_i)) then
      if (s_aes_validout = '1') then
        s_aes_dataout_d <= s_aes_dataout;
      end if;
    end if;
  end process outputregister;


  i_aes : aes_enc
    generic map (
      design_type => "ITER"
    )
    port map (
      reset_i  => reset_i,
      clk_i    => clk_i,
      key_i    => s_aes_key,
      data_i   => s_aes_datain,
      valid_i  => valid_i,
      accept_o => s_aes_accept,
      data_o   => s_aes_dataout,
      valid_o  => s_aes_validout,
      accept_i => accept_i
    );


end architecture rtl;