diff --git a/des/sim/tb_des.vhd b/des/sim/tb_des.vhd
new file mode 100644
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+++ b/des/sim/tb_des.vhd
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+-- ======================================================================
+-- DES encryption/decryption
+-- algorithm according to FIPS 46-3 specification
+-- Copyright (C) 2011 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
+-- ======================================================================
+
+
+-- Revision 1.0  2011/09/17
+-- Initial release
+
+
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.ALL;
+
+
+entity tb_des is
+end entity tb_des;
+
+
+architecture rtl of tb_des is
+
+
+  signal s_clk      : std_logic : := '0';
+  signal s_des1_key      : std_logic_vector(0 to 63);
+  signal s_des1_datain   : std_logic_vector(0 to 63);
+  signal s_des1_validin  : std_logic;
+  signal s_des1_dataout  : std_logic_vector(0 to 63);
+  signal s_des1_validout : std_logic;
+  
+  signal s_des2_key      : std_logic_vector(0 to 63);
+  signal s_des2_dataout  : std_logic_vector(0 to 63);
+  signal s_des2_validout : std_logic;
+
+
+  component des is
+    port (
+      clk_i       : IN  std_logic;
+      mode_i      : IN  std_logic;                  -- des-modus: 0 = encrypt, 1 = decrypt
+      key_i       : IN  std_logic_vector(0 TO 63);
+      data_i      : IN  std_logic_vector(0 TO 63);
+      valid_i     : IN  std_logic;
+      data_o      : OUT std_logic_vector(0 TO 63);
+      valid_o     : OUT std_logic
+    );
+  end component des;
+
+
+begin
+
+
+  s_clk <= not(s_clk) after 10 ns;
+  
+  
+  testinputP : process is
+  begin
+    for index in 0 to 31 loop
+      wait until s_clk = '1';
+      s_valid <= '1';
+      s_mode
+  end process testinputP;
+  
+
+  testoutputP : process is
+  begin
+    wait until s_clk = '1';
+  end process testoutputP;
+  
+
+
+  i1_des : des
+  port map (
+    clk_i    => s_clk,
+    mode_i   => '0',
+    key_i    => s_des1_key,
+    data_i   => s_des1_datain,
+    valid_i  => s_des1_validin,               
+    data_o   => s_des1_dataout,
+    valid_o  => s_des1_validout
+  );
+  
+  
+  i2_des : des
+  port map (
+    clk_i    => s_clk,
+    mode_i   => '1',
+    key_i    => s_des2_key,
+    data_i   => s_des1_dataout,
+    valid_i  => s_des1_validout,               
+    data_o   => s_des2_dataout,
+    valid_o  => s_des2_validout
+  );    
+
+
+end architecture rtl;
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