-- ----------------------------------------------------------------------
 -- FILE:    DESmedium.vhd
 -- DATE:    26 November 2000
 -- AUTHOR:  Antonio Esteves, GEC-DI-UM
 --
 -- DES CORE.
 --
 -- (c) 1999, The Free IP Project and David Kessner
 -- (c) 2000, Antonio Esteves, GEC-DI, University of Minho
 -- -----------------------------------------------------------------------

 library ieee;
 use     ieee.std_logic_1164.all;
 use     ieee.std_logic_arith.all;
 use     ieee.std_logic_unsigned.all;

 package DESlib is

  -- Inital permutation

  function DESip(din    :std_logic_vector(64 downto 1))
  return std_logic_vector;

  -- Final permutation

  function DESfp(din    :std_logic_vector(64 downto 1))
  return std_logic_vector;

  -- Key permutation, converts a 64 bit key into a 56 bit key,
  -- ignoring parity

  function DESpc1(din   :std_logic_vector (64 downto 1))
  return std_logic_vector;

  -- Compression permutation, converts a 56 bit key into a 48 bits

  function DESpc2(din   :std_logic_vector (56 downto 1))
  return std_logic_vector;

  -- Expansion permutation

  function DESep(din   :std_logic_vector (32 downto 1))
  return std_logic_vector;

  -- S-Box substitution, 48 bits in, 32 bits out

  function DESsbox(din   :std_logic_vector (47 downto 0))
  return std_logic_vector;

  -- P-Box permutation

  function DESpbox(din   :std_logic_vector (32 downto 1))
  return std_logic_vector;

  -- Key shift

  function DESkeyLshift (din : std_logic_vector (55 downto 0);
                         n   : std_logic_vector ( 4 downto 0))
  return std_logic_vector;

  function DESkeyRshift (din : std_logic_vector (55 downto 0);
                         n   : std_logic_vector ( 4 downto 0))
  return std_logic_vector;

 end DESlib;

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

 library ieee;
 use     ieee.std_logic_1164.all;
 use     ieee.std_logic_arith.all;
 use     ieee.std_logic_unsigned.all;
 library work;
 use     work.DESlib.all;

 package body DESlib is

  --------------------------------------------------------
  -- Inital permutation (IP)
  --------------------------------------------------------

  function DESip (
    din : std_logic_vector(64 downto 1)
    )
  return std_logic_vector is

    variable val    : std_logic_vector (64 downto 1);

  begin
    --     -----------------------
    --     58 50 42 34 26 18 10 2
    --     60 52 44 36 28 20 12 4
    --     62 54 46 38 30 22 14 6
    --     64 56 48 40 32 24 16 8
    --     57 49 41 33 25 17  9 1
    --     59 51 43 35 27 19 11 3
    --     61 53 45 37 29 21 13 5
    --     63 55 47 39 31 23 15 7
    --     -----------------------

    val :=  din(7 ) & din(15) & din(23) & din(31) & din(39) & din(47) &
            din(55) & din(63) & din(5 ) & din(13) & din(21) & din(29) &
            din(37) & din(45) & din(53) & din(61) & din(3 ) & din(11) &
            din(19) & din(27) & din(35) & din(43) & din(51) & din(59) &
            din(1 ) & din(9 ) & din(17) & din(25) & din(33) & din(41) &
            din(49) & din(57) & din(8 ) & din(16) & din(24) & din(32) &
            din(40) & din(48) & din(56) & din(64) & din(6 ) & din(14) &
            din(22) & din(30) & din(38) & din(46) & din(54) & din(62) &
            din(4 ) & din(12) & din(20) & din(28) & din(36) & din(44) &
            din(52) & din(60) & din(2 ) & din(10) & din(18) & din(26) &
            din(34) & din(42) & din(50) & din(58) ;

    return val;
  end DESip;

  --------------------------------------------------------
  -- Final permutation (IP^(-1) or FP)
  --------------------------------------------------------

  function DESfp(
    din : std_logic_vector(64 downto 1))
  return std_logic_vector is

    variable val    : std_logic_vector (64 downto 1);

  begin

    --     ---------------------------
    --     40 8 48 16 56 24 64 32
    --     39 7 47 15 55 23 63 31
    --     38 6 46 14 54 22 62 30
    --     37 5 45 13 53 21 61 29
    --     36 4 44 12 52 20 60 28
    --     35 3 43 11 51 19 59 27
    --     34 2 42 10 50 18 58 26
    --     33 1 41  9 49 17 57 25
    --     ---------------------------

    val :=  din(25) & din(57) & din(17) & din(49) & din(9 ) & din(41) &
            din(1 ) & din(33) & din(26) & din(58) & din(18) & din(50) &
            din(10) & din(42) & din(2 ) & din(34) & din(27) & din(59) &
            din(19) & din(51) & din(11) & din(43) & din(3 ) & din(35) &
            din(28) & din(60) & din(20) & din(52) & din(12) & din(44) &
            din(4 ) & din(36) & din(29) & din(61) & din(21) & din(53) &
            din(13) & din(45) & din(5 ) & din(37) & din(30) & din(62) &
            din(22) & din(54) & din(14) & din(46) & din(6 ) & din(38) &
            din(31) & din(63) & din(23) & din(55) & din(15) & din(47) &
            din(7 ) & din(39) & din(32) & din(64) & din(24) & din(56) &
            din(16) & din(48) & din(8 ) & din(40) ;

    return val;
  end DESfp;

  --------------------------------------------------------
  -- Permutation choice 1 (PC1): converts a 64 bit key into a 56 bit key,
  --                             ignoring parity
  --------------------------------------------------------

  function DESpc1 (
    din  : std_logic_vector (64 downto 1))
  return std_logic_vector is

    variable val : std_logic_vector (55 downto 0);

  begin

    --     ---------------------------
    --     57 49 41 33 25 17  9
    --      1 58 50 42 34 26 18
    --     10  2 59 51 43 35 27
    --     19 11  3 60 52 44 36
    --     63 55 47 39 31 23 15
    --      7 62 54 46 38 30 22
    --     14  6 61 53 45 37 29
    --     21 13  5 28 20 12  4
    --     ---------------------------

    val :=  din(4 ) & din(12) & din(20) & din(28) & din(5 ) & din(13) &
            din(21) & din(29) & din(37) & din(45) & din(53) & din(61) &
            din(6 ) & din(14) & din(22) & din(30) & din(38) & din(46) &
            din(54) & din(62) & din(7 ) & din(15) & din(23) & din(31) &
            din(39) & din(47) & din(55) & din(63) & din(36) & din(44) &
            din(52) & din(60) & din(3 ) & din(11) & din(19) & din(27) &
            din(35) & din(43) & din(51) & din(59) & din(2 ) & din(10) &
            din(18) & din(26) & din(34) & din(42) & din(50) & din(58) &
            din(1 ) & din(9 ) & din(17) & din(25) & din(33) & din(41) &
            din(49) & din(57);

    return val;
  end DESpc1;

  --------------------------------------------------------
  -- Compression permutation (C-box) / Permutation choice 2 (PC2):
  -- converts a 56 bit key into a 48 bits
  --------------------------------------------------------

  function DESpc2 (
    din  : std_logic_vector (56 downto 1))
  return std_logic_vector is

    variable val  : std_logic_vector (48 downto 1);

  begin

    --     ---------------------------
    --     14 17 11 24  1  5
    --      3 28 15  6 21 10
    --     23 19 12  4 26  8
    --     16  7 27 20 13  2
    --     41 52 31 37 47 55
    --     30 40 51 45 33 48
    --     44 49 39 56 34 53
    --     46 42 50 36 29 32
    --     ---------------------------

    val := din(32) & din(29) & din(36) & din(50) & din(42) & din(46) &
           din(53) & din(34) & din(56) & din(39) & din(49) & din(44) &
           din(48) & din(33) & din(45) & din(51) & din(40) & din(30) &
           din(55) & din(47) & din(37) & din(31) & din(52) & din(41) &
           din(2 ) & din(13) & din(20) & din(27) & din(7 ) & din(16) &
           din(8 ) & din(26) & din(4 ) & din(12) & din(19) & din(23) &
           din(10) & din(21) & din(6 ) & din(15) & din(28) & din(3 ) &
           din(5 ) & din(1 ) & din(24) & din(11) & din(17) & din(14) ;

    return val;
  end DESpc2;

  --------------------------------------------------------
  -- E operator: expands a permutation from 32 to 48 bits
  --------------------------------------------------------

  function DESep (
    din  : std_logic_vector (32 downto 1))
  return std_logic_vector is

    variable val  : std_logic_vector (48 downto 1);

  begin

    --     ---------------------------
    --     32  1  2  3  4  5
    --      4  5  6  7  8  9
    --      8  9 10 11 12 13
    --     12 13 14 15 16 17
    --     16 17 18 19 20 21
    --     20 21 22 23 24 25
    --     24 25 26 27 28 29
    --     28 29 30 31 32  1
    --     ---------------------------

    val := din(1 ) & din(32) & din(31) & din(30) & din(29) & din(28) &
           din(29) & din(28) & din(27) & din(26) & din(25) & din(24) &
           din(25) & din(24) & din(23) & din(22) & din(21) & din(20) &
           din(21) & din(20) & din(19) & din(18) & din(17) & din(16) &
           din(17) & din(16) & din(15) & din(14) & din(13) & din(12) &
           din(13) & din(12) & din(11) & din(10) & din(9 ) & din(8 ) &
           din(9 ) & din(8 ) & din(7 ) & din(6 ) & din(5 ) & din(4 ) &
           din(5 ) & din(4 ) & din(3 ) & din(2 ) & din(1 ) & din(32) ;

      return val;
  end DESep;

  ------------------------------------------------------------------------
  -- Substitution tables (S-Box 1:8):
  -- all together have 48 bits input, 32 bits output
  ------------------------------------------------------------------------

  function DESsbox (
    din  : std_logic_vector (47 downto 0))
  return std_logic_vector is

    variable val  : std_logic_vector (31 downto 0);

  begin

    -- SBOX 8

    case din( 5 downto  0) is
      when "000000" =>  val(3 downto 0) := "1101";
      when "000001" =>  val(3 downto 0) := "0001";
      when "000010" =>  val(3 downto 0) := "0010";
      when "000011" =>  val(3 downto 0) := "1111";
      when "000100" =>  val(3 downto 0) := "1000";
      when "000101" =>  val(3 downto 0) := "1101";
      when "000110" =>  val(3 downto 0) := "0100";
      when "000111" =>  val(3 downto 0) := "1000";
      when "001000" =>  val(3 downto 0) := "0110";
      when "001001" =>  val(3 downto 0) := "1010";
      when "001010" =>  val(3 downto 0) := "1111";
      when "001011" =>  val(3 downto 0) := "0011";
      when "001100" =>  val(3 downto 0) := "1011";
      when "001101" =>  val(3 downto 0) := "0111";
      when "001110" =>  val(3 downto 0) := "0001";
      when "001111" =>  val(3 downto 0) := "0100";
      when "010000" =>  val(3 downto 0) := "1010";
      when "010001" =>  val(3 downto 0) := "1100";
      when "010010" =>  val(3 downto 0) := "1001";
      when "010011" =>  val(3 downto 0) := "0101";
      when "010100" =>  val(3 downto 0) := "0011";
      when "010101" =>  val(3 downto 0) := "0110";
      when "010110" =>  val(3 downto 0) := "1110";
      when "010111" =>  val(3 downto 0) := "1011";
      when "011000" =>  val(3 downto 0) := "0101";
      when "011001" =>  val(3 downto 0) := "0000";
      when "011010" =>  val(3 downto 0) := "0000";
      when "011011" =>  val(3 downto 0) := "1110";
      when "011100" =>  val(3 downto 0) := "1100";
      when "011101" =>  val(3 downto 0) := "1001";
      when "011110" =>  val(3 downto 0) := "0111";
      when "011111" =>  val(3 downto 0) := "0010";
      when "100000" =>  val(3 downto 0) := "0111";
      when "100001" =>  val(3 downto 0) := "0010";
      when "100010" =>  val(3 downto 0) := "1011";
      when "100011" =>  val(3 downto 0) := "0001";
      when "100100" =>  val(3 downto 0) := "0100";
      when "100101" =>  val(3 downto 0) := "1110";
      when "100110" =>  val(3 downto 0) := "0001";
      when "100111" =>  val(3 downto 0) := "0111";
      when "101000" =>  val(3 downto 0) := "1001";
      when "101001" =>  val(3 downto 0) := "0100";
      when "101010" =>  val(3 downto 0) := "1100";
      when "101011" =>  val(3 downto 0) := "1010";
      when "101100" =>  val(3 downto 0) := "1110";
      when "101101" =>  val(3 downto 0) := "1000";
      when "101110" =>  val(3 downto 0) := "0010";
      when "101111" =>  val(3 downto 0) := "1101";
      when "110000" =>  val(3 downto 0) := "0000";
      when "110001" =>  val(3 downto 0) := "1111";
      when "110010" =>  val(3 downto 0) := "0110";
      when "110011" =>  val(3 downto 0) := "1100";
      when "110100" =>  val(3 downto 0) := "1010";
      when "110101" =>  val(3 downto 0) := "1001";
      when "110110" =>  val(3 downto 0) := "1101";
      when "110111" =>  val(3 downto 0) := "0000";
      when "111000" =>  val(3 downto 0) := "1111";
      when "111001" =>  val(3 downto 0) := "0011";
      when "111010" =>  val(3 downto 0) := "0011";
      when "111011" =>  val(3 downto 0) := "0101";
      when "111100" =>  val(3 downto 0) := "0101";
      when "111101" =>  val(3 downto 0) := "0110";
      when "111110" =>  val(3 downto 0) := "1000";
      when "111111" =>  val(3 downto 0) := "1011";
      when others   =>  val(3 downto 0) := "1011";
    end case;

    -- SBOX 7

    case din(11 downto  6) is
      when "000000" =>  val(7 downto 4) := "0100";
      when "000001" =>  val(7 downto 4) := "1101";
      when "000010" =>  val(7 downto 4) := "1011";
      when "000011" =>  val(7 downto 4) := "0000";
      when "000100" =>  val(7 downto 4) := "0010";
      when "000101" =>  val(7 downto 4) := "1011";
      when "000110" =>  val(7 downto 4) := "1110";
      when "000111" =>  val(7 downto 4) := "0111";
      when "001000" =>  val(7 downto 4) := "1111";
      when "001001" =>  val(7 downto 4) := "0100";
      when "001010" =>  val(7 downto 4) := "0000";
      when "001011" =>  val(7 downto 4) := "1001";
      when "001100" =>  val(7 downto 4) := "1000";
      when "001101" =>  val(7 downto 4) := "0001";
      when "001110" =>  val(7 downto 4) := "1101";
      when "001111" =>  val(7 downto 4) := "1010";
      when "010000" =>  val(7 downto 4) := "0011";
      when "010001" =>  val(7 downto 4) := "1110";
      when "010010" =>  val(7 downto 4) := "1100";
      when "010011" =>  val(7 downto 4) := "0011";
      when "010100" =>  val(7 downto 4) := "1001";
      when "010101" =>  val(7 downto 4) := "0101";
      when "010110" =>  val(7 downto 4) := "0111";
      when "010111" =>  val(7 downto 4) := "1100";
      when "011000" =>  val(7 downto 4) := "0101";
      when "011001" =>  val(7 downto 4) := "0010";
      when "011010" =>  val(7 downto 4) := "1010";
      when "011011" =>  val(7 downto 4) := "1111";
      when "011100" =>  val(7 downto 4) := "0110";
      when "011101" =>  val(7 downto 4) := "1000";
      when "011110" =>  val(7 downto 4) := "0001";
      when "011111" =>  val(7 downto 4) := "0110";
      when "100000" =>  val(7 downto 4) := "0001";
      when "100001" =>  val(7 downto 4) := "0110";
      when "100010" =>  val(7 downto 4) := "0100";
      when "100011" =>  val(7 downto 4) := "1011";
      when "100100" =>  val(7 downto 4) := "1011";
      when "100101" =>  val(7 downto 4) := "1101";
      when "100110" =>  val(7 downto 4) := "1101";
      when "100111" =>  val(7 downto 4) := "1000";
      when "101000" =>  val(7 downto 4) := "1100";
      when "101001" =>  val(7 downto 4) := "0001";
      when "101010" =>  val(7 downto 4) := "0011";
      when "101011" =>  val(7 downto 4) := "0100";
      when "101100" =>  val(7 downto 4) := "0111";
      when "101101" =>  val(7 downto 4) := "1010";
      when "101110" =>  val(7 downto 4) := "1110";
      when "101111" =>  val(7 downto 4) := "0111";
      when "110000" =>  val(7 downto 4) := "1010";
      when "110001" =>  val(7 downto 4) := "1001";
      when "110010" =>  val(7 downto 4) := "1111";
      when "110011" =>  val(7 downto 4) := "0101";
      when "110100" =>  val(7 downto 4) := "0110";
      when "110101" =>  val(7 downto 4) := "0000";
      when "110110" =>  val(7 downto 4) := "1000";
      when "110111" =>  val(7 downto 4) := "1111";
      when "111000" =>  val(7 downto 4) := "0000";
      when "111001" =>  val(7 downto 4) := "1110";
      when "111010" =>  val(7 downto 4) := "0101";
      when "111011" =>  val(7 downto 4) := "0010";
      when "111100" =>  val(7 downto 4) := "1001";
      when "111101" =>  val(7 downto 4) := "0011";
      when "111110" =>  val(7 downto 4) := "0010";
      when "111111" =>  val(7 downto 4) := "1100";
      when others   =>  val(7 downto 4) := "1100";
    end case;

    -- SBOX 6

    case din(17 downto 12) is
      when "000000" =>  val(11 downto 8) := "1100";
      when "000001" =>  val(11 downto 8) := "1010";
      when "000010" =>  val(11 downto 8) := "0001";
      when "000011" =>  val(11 downto 8) := "1111";
      when "000100" =>  val(11 downto 8) := "1010";
      when "000101" =>  val(11 downto 8) := "0100";
      when "000110" =>  val(11 downto 8) := "1111";
      when "000111" =>  val(11 downto 8) := "0010";
      when "001000" =>  val(11 downto 8) := "1001";
      when "001001" =>  val(11 downto 8) := "0111";
      when "001010" =>  val(11 downto 8) := "0010";
      when "001011" =>  val(11 downto 8) := "1100";
      when "001100" =>  val(11 downto 8) := "0110";
      when "001101" =>  val(11 downto 8) := "1001";
      when "001110" =>  val(11 downto 8) := "1000";
      when "001111" =>  val(11 downto 8) := "0101";
      when "010000" =>  val(11 downto 8) := "0000";
      when "010001" =>  val(11 downto 8) := "0110";
      when "010010" =>  val(11 downto 8) := "1101";
      when "010011" =>  val(11 downto 8) := "0001";
      when "010100" =>  val(11 downto 8) := "0011";
      when "010101" =>  val(11 downto 8) := "1101";
      when "010110" =>  val(11 downto 8) := "0100";
      when "010111" =>  val(11 downto 8) := "1110";
      when "011000" =>  val(11 downto 8) := "1110";
      when "011001" =>  val(11 downto 8) := "0000";
      when "011010" =>  val(11 downto 8) := "0111";
      when "011011" =>  val(11 downto 8) := "1011";
      when "011100" =>  val(11 downto 8) := "0101";
      when "011101" =>  val(11 downto 8) := "0011";
      when "011110" =>  val(11 downto 8) := "1011";
      when "011111" =>  val(11 downto 8) := "1000";
      when "100000" =>  val(11 downto 8) := "1001";
      when "100001" =>  val(11 downto 8) := "0100";
      when "100010" =>  val(11 downto 8) := "1110";
      when "100011" =>  val(11 downto 8) := "0011";
      when "100100" =>  val(11 downto 8) := "1111";
      when "100101" =>  val(11 downto 8) := "0010";
      when "100110" =>  val(11 downto 8) := "0101";
      when "100111" =>  val(11 downto 8) := "1100";
      when "101000" =>  val(11 downto 8) := "0010";
      when "101001" =>  val(11 downto 8) := "1001";
      when "101010" =>  val(11 downto 8) := "1000";
      when "101011" =>  val(11 downto 8) := "0101";
      when "101100" =>  val(11 downto 8) := "1100";
      when "101101" =>  val(11 downto 8) := "1111";
      when "101110" =>  val(11 downto 8) := "0011";
      when "101111" =>  val(11 downto 8) := "1010";
      when "110000" =>  val(11 downto 8) := "0111";
      when "110001" =>  val(11 downto 8) := "1011";
      when "110010" =>  val(11 downto 8) := "0000";
      when "110011" =>  val(11 downto 8) := "1110";
      when "110100" =>  val(11 downto 8) := "0100";
      when "110101" =>  val(11 downto 8) := "0001";
      when "110110" =>  val(11 downto 8) := "1010";
      when "110111" =>  val(11 downto 8) := "0111";
      when "111000" =>  val(11 downto 8) := "0001";
      when "111001" =>  val(11 downto 8) := "0110";
      when "111010" =>  val(11 downto 8) := "1101";
      when "111011" =>  val(11 downto 8) := "0000";
      when "111100" =>  val(11 downto 8) := "1011";
      when "111101" =>  val(11 downto 8) := "1000";
      when "111110" =>  val(11 downto 8) := "0110";
      when "111111" =>  val(11 downto 8) := "1101";
      when others   =>  val(11 downto 8) := "1101";
    end case;

    -- SBOX 5

    case din(23 downto 18) is
      when "000000" =>  val(15 downto 12) := "0010";
      when "000001" =>  val(15 downto 12) := "1110";
      when "000010" =>  val(15 downto 12) := "1100";
      when "000011" =>  val(15 downto 12) := "1011";
      when "000100" =>  val(15 downto 12) := "0100";
      when "000101" =>  val(15 downto 12) := "0010";
      when "000110" =>  val(15 downto 12) := "0001";
      when "000111" =>  val(15 downto 12) := "1100";
      when "001000" =>  val(15 downto 12) := "0111";
      when "001001" =>  val(15 downto 12) := "0100";
      when "001010" =>  val(15 downto 12) := "1010";
      when "001011" =>  val(15 downto 12) := "0111";
      when "001100" =>  val(15 downto 12) := "1011";
      when "001101" =>  val(15 downto 12) := "1101";
      when "001110" =>  val(15 downto 12) := "0110";
      when "001111" =>  val(15 downto 12) := "0001";
      when "010000" =>  val(15 downto 12) := "1000";
      when "010001" =>  val(15 downto 12) := "0101";
      when "010010" =>  val(15 downto 12) := "0101";
      when "010011" =>  val(15 downto 12) := "0000";
      when "010100" =>  val(15 downto 12) := "0011";
      when "010101" =>  val(15 downto 12) := "1111";
      when "010110" =>  val(15 downto 12) := "1111";
      when "010111" =>  val(15 downto 12) := "1010";
      when "011000" =>  val(15 downto 12) := "1101";
      when "011001" =>  val(15 downto 12) := "0011";
      when "011010" =>  val(15 downto 12) := "0000";
      when "011011" =>  val(15 downto 12) := "1001";
      when "011100" =>  val(15 downto 12) := "1110";
      when "011101" =>  val(15 downto 12) := "1000";
      when "011110" =>  val(15 downto 12) := "1001";
      when "011111" =>  val(15 downto 12) := "0110";
      when "100000" =>  val(15 downto 12) := "0100";
      when "100001" =>  val(15 downto 12) := "1011";
      when "100010" =>  val(15 downto 12) := "0010";
      when "100011" =>  val(15 downto 12) := "1000";
      when "100100" =>  val(15 downto 12) := "0001";
      when "100101" =>  val(15 downto 12) := "1100";
      when "100110" =>  val(15 downto 12) := "1011";
      when "100111" =>  val(15 downto 12) := "0111";
      when "101000" =>  val(15 downto 12) := "1010";
      when "101001" =>  val(15 downto 12) := "0001";
      when "101010" =>  val(15 downto 12) := "1101";
      when "101011" =>  val(15 downto 12) := "1110";
      when "101100" =>  val(15 downto 12) := "0111";
      when "101101" =>  val(15 downto 12) := "0010";
      when "101110" =>  val(15 downto 12) := "1000";
      when "101111" =>  val(15 downto 12) := "1101";
      when "110000" =>  val(15 downto 12) := "1111";
      when "110001" =>  val(15 downto 12) := "0110";
      when "110010" =>  val(15 downto 12) := "1001";
      when "110011" =>  val(15 downto 12) := "1111";
      when "110100" =>  val(15 downto 12) := "1100";
      when "110101" =>  val(15 downto 12) := "0000";
      when "110110" =>  val(15 downto 12) := "0101";
      when "110111" =>  val(15 downto 12) := "1001";
      when "111000" =>  val(15 downto 12) := "0110";
      when "111001" =>  val(15 downto 12) := "1010";
      when "111010" =>  val(15 downto 12) := "0011";
      when "111011" =>  val(15 downto 12) := "0100";
      when "111100" =>  val(15 downto 12) := "0000";
      when "111101" =>  val(15 downto 12) := "0101";
      when "111110" =>  val(15 downto 12) := "1110";
      when "111111" =>  val(15 downto 12) := "0011";
      when others   =>  val(15 downto 12) := "0011";
    end case;

    -- SBOX 4

    case din(29 downto 24) is
      when "000000" =>  val(19 downto 16) := "0111";
      when "000001" =>  val(19 downto 16) := "1101";
      when "000010" =>  val(19 downto 16) := "1101";
      when "000011" =>  val(19 downto 16) := "1000";
      when "000100" =>  val(19 downto 16) := "1110";
      when "000101" =>  val(19 downto 16) := "1011";
      when "000110" =>  val(19 downto 16) := "0011";
      when "000111" =>  val(19 downto 16) := "0101";
      when "001000" =>  val(19 downto 16) := "0000";
      when "001001" =>  val(19 downto 16) := "0110";
      when "001010" =>  val(19 downto 16) := "0110";
      when "001011" =>  val(19 downto 16) := "1111";
      when "001100" =>  val(19 downto 16) := "1001";
      when "001101" =>  val(19 downto 16) := "0000";
      when "001110" =>  val(19 downto 16) := "1010";
      when "001111" =>  val(19 downto 16) := "0011";
      when "010000" =>  val(19 downto 16) := "0001";
      when "010001" =>  val(19 downto 16) := "0100";
      when "010010" =>  val(19 downto 16) := "0010";
      when "010011" =>  val(19 downto 16) := "0111";
      when "010100" =>  val(19 downto 16) := "1000";
      when "010101" =>  val(19 downto 16) := "0010";
      when "010110" =>  val(19 downto 16) := "0101";
      when "010111" =>  val(19 downto 16) := "1100";
      when "011000" =>  val(19 downto 16) := "1011";
      when "011001" =>  val(19 downto 16) := "0001";
      when "011010" =>  val(19 downto 16) := "1100";
      when "011011" =>  val(19 downto 16) := "1010";
      when "011100" =>  val(19 downto 16) := "0100";
      when "011101" =>  val(19 downto 16) := "1110";
      when "011110" =>  val(19 downto 16) := "1111";
      when "011111" =>  val(19 downto 16) := "1001";
      when "100000" =>  val(19 downto 16) := "1010";
      when "100001" =>  val(19 downto 16) := "0011";
      when "100010" =>  val(19 downto 16) := "0110";
      when "100011" =>  val(19 downto 16) := "1111";
      when "100100" =>  val(19 downto 16) := "1001";
      when "100101" =>  val(19 downto 16) := "0000";
      when "100110" =>  val(19 downto 16) := "0000";
      when "100111" =>  val(19 downto 16) := "0110";
      when "101000" =>  val(19 downto 16) := "1100";
      when "101001" =>  val(19 downto 16) := "1010";
      when "101010" =>  val(19 downto 16) := "1011";
      when "101011" =>  val(19 downto 16) := "0001";
      when "101100" =>  val(19 downto 16) := "0111";
      when "101101" =>  val(19 downto 16) := "1101";
      when "101110" =>  val(19 downto 16) := "1101";
      when "101111" =>  val(19 downto 16) := "1000";
      when "110000" =>  val(19 downto 16) := "1111";
      when "110001" =>  val(19 downto 16) := "1001";
      when "110010" =>  val(19 downto 16) := "0001";
      when "110011" =>  val(19 downto 16) := "0100";
      when "110100" =>  val(19 downto 16) := "0011";
      when "110101" =>  val(19 downto 16) := "0101";
      when "110110" =>  val(19 downto 16) := "1110";
      when "110111" =>  val(19 downto 16) := "1011";
      when "111000" =>  val(19 downto 16) := "0101";
      when "111001" =>  val(19 downto 16) := "1100";
      when "111010" =>  val(19 downto 16) := "0010";
      when "111011" =>  val(19 downto 16) := "0111";
      when "111100" =>  val(19 downto 16) := "1000";
      when "111101" =>  val(19 downto 16) := "0010";
      when "111110" =>  val(19 downto 16) := "0100";
      when "111111" =>  val(19 downto 16) := "1110";
      when others   =>  val(19 downto 16) := "1110";
    end case;

    -- SBOX 3

    case din(35 downto 30) is
      when "000000" =>  val(23 downto 20) := "1010";
      when "000001" =>  val(23 downto 20) := "1101";
      when "000010" =>  val(23 downto 20) := "0000";
      when "000011" =>  val(23 downto 20) := "0111";
      when "000100" =>  val(23 downto 20) := "1001";
      when "000101" =>  val(23 downto 20) := "0000";
      when "000110" =>  val(23 downto 20) := "1110";
      when "000111" =>  val(23 downto 20) := "1001";
      when "001000" =>  val(23 downto 20) := "0110";
      when "001001" =>  val(23 downto 20) := "0011";
      when "001010" =>  val(23 downto 20) := "0011";
      when "001011" =>  val(23 downto 20) := "0100";
      when "001100" =>  val(23 downto 20) := "1111";
      when "001101" =>  val(23 downto 20) := "0110";
      when "001110" =>  val(23 downto 20) := "0101";
      when "001111" =>  val(23 downto 20) := "1010";
      when "010000" =>  val(23 downto 20) := "0001";
      when "010001" =>  val(23 downto 20) := "0010";
      when "010010" =>  val(23 downto 20) := "1101";
      when "010011" =>  val(23 downto 20) := "1000";
      when "010100" =>  val(23 downto 20) := "1100";
      when "010101" =>  val(23 downto 20) := "0101";
      when "010110" =>  val(23 downto 20) := "0111";
      when "010111" =>  val(23 downto 20) := "1110";
      when "011000" =>  val(23 downto 20) := "1011";
      when "011001" =>  val(23 downto 20) := "1100";
      when "011010" =>  val(23 downto 20) := "0100";
      when "011011" =>  val(23 downto 20) := "1011";
      when "011100" =>  val(23 downto 20) := "0010";
      when "011101" =>  val(23 downto 20) := "1111";
      when "011110" =>  val(23 downto 20) := "1000";
      when "011111" =>  val(23 downto 20) := "0001";
      when "100000" =>  val(23 downto 20) := "1101";
      when "100001" =>  val(23 downto 20) := "0001";
      when "100010" =>  val(23 downto 20) := "0110";
      when "100011" =>  val(23 downto 20) := "1010";
      when "100100" =>  val(23 downto 20) := "0100";
      when "100101" =>  val(23 downto 20) := "1101";
      when "100110" =>  val(23 downto 20) := "1001";
      when "100111" =>  val(23 downto 20) := "0000";
      when "101000" =>  val(23 downto 20) := "1000";
      when "101001" =>  val(23 downto 20) := "0110";
      when "101010" =>  val(23 downto 20) := "1111";
      when "101011" =>  val(23 downto 20) := "1001";
      when "101100" =>  val(23 downto 20) := "0011";
      when "101101" =>  val(23 downto 20) := "1000";
      when "101110" =>  val(23 downto 20) := "0000";
      when "101111" =>  val(23 downto 20) := "0111";
      when "110000" =>  val(23 downto 20) := "1011";
      when "110001" =>  val(23 downto 20) := "0100";
      when "110010" =>  val(23 downto 20) := "0001";
      when "110011" =>  val(23 downto 20) := "1111";
      when "110100" =>  val(23 downto 20) := "0010";
      when "110101" =>  val(23 downto 20) := "1110";
      when "110110" =>  val(23 downto 20) := "1100";
      when "110111" =>  val(23 downto 20) := "0011";
      when "111000" =>  val(23 downto 20) := "0101";
      when "111001" =>  val(23 downto 20) := "1011";
      when "111010" =>  val(23 downto 20) := "1010";
      when "111011" =>  val(23 downto 20) := "0101";
      when "111100" =>  val(23 downto 20) := "1110";
      when "111101" =>  val(23 downto 20) := "0010";
      when "111110" =>  val(23 downto 20) := "0111";
      when "111111" =>  val(23 downto 20) := "1100";
      when others   =>  val(23 downto 20) := "1100";
    end case;

    -- SBOX 2

    case din(41 downto 36) is
      when "000000" =>  val(27 downto 24) := "1111";
      when "000001" =>  val(27 downto 24) := "0011";
      when "000010" =>  val(27 downto 24) := "0001";
      when "000011" =>  val(27 downto 24) := "1101";
      when "000100" =>  val(27 downto 24) := "1000";
      when "000101" =>  val(27 downto 24) := "0100";
      when "000110" =>  val(27 downto 24) := "1110";
      when "000111" =>  val(27 downto 24) := "0111";
      when "001000" =>  val(27 downto 24) := "0110";
      when "001001" =>  val(27 downto 24) := "1111";
      when "001010" =>  val(27 downto 24) := "1011";
      when "001011" =>  val(27 downto 24) := "0010";
      when "001100" =>  val(27 downto 24) := "0011";
      when "001101" =>  val(27 downto 24) := "1000";
      when "001110" =>  val(27 downto 24) := "0100";
      when "001111" =>  val(27 downto 24) := "1110";
      when "010000" =>  val(27 downto 24) := "1001";
      when "010001" =>  val(27 downto 24) := "1100";
      when "010010" =>  val(27 downto 24) := "0111";
      when "010011" =>  val(27 downto 24) := "0000";
      when "010100" =>  val(27 downto 24) := "0010";
      when "010101" =>  val(27 downto 24) := "0001";
      when "010110" =>  val(27 downto 24) := "1101";
      when "010111" =>  val(27 downto 24) := "1010";
      when "011000" =>  val(27 downto 24) := "1100";
      when "011001" =>  val(27 downto 24) := "0110";
      when "011010" =>  val(27 downto 24) := "0000";
      when "011011" =>  val(27 downto 24) := "1001";
      when "011100" =>  val(27 downto 24) := "0101";
      when "011101" =>  val(27 downto 24) := "1011";
      when "011110" =>  val(27 downto 24) := "1010";
      when "011111" =>  val(27 downto 24) := "0101";
      when "100000" =>  val(27 downto 24) := "0000";
      when "100001" =>  val(27 downto 24) := "1101";
      when "100010" =>  val(27 downto 24) := "1110";
      when "100011" =>  val(27 downto 24) := "1000";
      when "100100" =>  val(27 downto 24) := "0111";
      when "100101" =>  val(27 downto 24) := "1010";
      when "100110" =>  val(27 downto 24) := "1011";
      when "100111" =>  val(27 downto 24) := "0001";
      when "101000" =>  val(27 downto 24) := "1010";
      when "101001" =>  val(27 downto 24) := "0011";
      when "101010" =>  val(27 downto 24) := "0100";
      when "101011" =>  val(27 downto 24) := "1111";
      when "101100" =>  val(27 downto 24) := "1101";
      when "101101" =>  val(27 downto 24) := "0100";
      when "101110" =>  val(27 downto 24) := "0001";
      when "101111" =>  val(27 downto 24) := "0010";
      when "110000" =>  val(27 downto 24) := "0101";
      when "110001" =>  val(27 downto 24) := "1011";
      when "110010" =>  val(27 downto 24) := "1000";
      when "110011" =>  val(27 downto 24) := "0110";
      when "110100" =>  val(27 downto 24) := "1100";
      when "110101" =>  val(27 downto 24) := "0111";
      when "110110" =>  val(27 downto 24) := "0110";
      when "110111" =>  val(27 downto 24) := "1100";
      when "111000" =>  val(27 downto 24) := "1001";
      when "111001" =>  val(27 downto 24) := "0000";
      when "111010" =>  val(27 downto 24) := "0011";
      when "111011" =>  val(27 downto 24) := "0101";
      when "111100" =>  val(27 downto 24) := "0010";
      when "111101" =>  val(27 downto 24) := "1110";
      when "111110" =>  val(27 downto 24) := "1111";
      when "111111" =>  val(27 downto 24) := "1001";
      when others   =>  val(27 downto 24) := "1001";
    end case;

    -- SBOX 1

    case din(47 downto 42) is
      when "000000" =>  val(31 downto 28) := "1110";
      when "000001" =>  val(31 downto 28) := "0000";
      when "000010" =>  val(31 downto 28) := "0100";
      when "000011" =>  val(31 downto 28) := "1111";
      when "000100" =>  val(31 downto 28) := "1101";
      when "000101" =>  val(31 downto 28) := "0111";
      when "000110" =>  val(31 downto 28) := "0001";
      when "000111" =>  val(31 downto 28) := "0100";
      when "001000" =>  val(31 downto 28) := "0010";
      when "001001" =>  val(31 downto 28) := "1110";
      when "001010" =>  val(31 downto 28) := "1111";
      when "001011" =>  val(31 downto 28) := "0010";
      when "001100" =>  val(31 downto 28) := "1011";
      when "001101" =>  val(31 downto 28) := "1101";
      when "001110" =>  val(31 downto 28) := "1000";
      when "001111" =>  val(31 downto 28) := "0001";
      when "010000" =>  val(31 downto 28) := "0011";
      when "010001" =>  val(31 downto 28) := "1010";
      when "010010" =>  val(31 downto 28) := "1010";
      when "010011" =>  val(31 downto 28) := "0110";
      when "010100" =>  val(31 downto 28) := "0110";
      when "010101" =>  val(31 downto 28) := "1100";
      when "010110" =>  val(31 downto 28) := "1100";
      when "010111" =>  val(31 downto 28) := "1011";
      when "011000" =>  val(31 downto 28) := "0101";
      when "011001" =>  val(31 downto 28) := "1001";
      when "011010" =>  val(31 downto 28) := "1001";
      when "011011" =>  val(31 downto 28) := "0101";
      when "011100" =>  val(31 downto 28) := "0000";
      when "011101" =>  val(31 downto 28) := "0011";
      when "011110" =>  val(31 downto 28) := "0111";
      when "011111" =>  val(31 downto 28) := "1000";
      when "100000" =>  val(31 downto 28) := "0100";
      when "100001" =>  val(31 downto 28) := "1111";
      when "100010" =>  val(31 downto 28) := "0001";
      when "100011" =>  val(31 downto 28) := "1100";
      when "100100" =>  val(31 downto 28) := "1110";
      when "100101" =>  val(31 downto 28) := "1000";
      when "100110" =>  val(31 downto 28) := "1000";
      when "100111" =>  val(31 downto 28) := "0010";
      when "101000" =>  val(31 downto 28) := "1101";
      when "101001" =>  val(31 downto 28) := "0100";
      when "101010" =>  val(31 downto 28) := "0110";
      when "101011" =>  val(31 downto 28) := "1001";
      when "101100" =>  val(31 downto 28) := "0010";
      when "101101" =>  val(31 downto 28) := "0001";
      when "101110" =>  val(31 downto 28) := "1011";
      when "101111" =>  val(31 downto 28) := "0111";
      when "110000" =>  val(31 downto 28) := "1111";
      when "110001" =>  val(31 downto 28) := "0101";
      when "110010" =>  val(31 downto 28) := "1100";
      when "110011" =>  val(31 downto 28) := "1011";
      when "110100" =>  val(31 downto 28) := "1001";
      when "110101" =>  val(31 downto 28) := "0011";
      when "110110" =>  val(31 downto 28) := "0111";
      when "110111" =>  val(31 downto 28) := "1110";
      when "111000" =>  val(31 downto 28) := "0011";
      when "111001" =>  val(31 downto 28) := "1010";
      when "111010" =>  val(31 downto 28) := "1010";
      when "111011" =>  val(31 downto 28) := "0000";
      when "111100" =>  val(31 downto 28) := "0101";
      when "111101" =>  val(31 downto 28) := "0110";
      when "111110" =>  val(31 downto 28) := "0000";
      when "111111" =>  val(31 downto 28) := "1101";
      when others   =>  val(31 downto 28) := "1101";
    end case;

    return val;
  end DESsbox;

  --------------------------------------------------------
  -- Permutation P (P-Box)
  --------------------------------------------------------

  function DESpbox (
    din  : std_logic_vector (32 downto 1))
  return std_logic_vector is

    variable val  : std_logic_vector (32 downto 1);

  begin

    --     ---------------------------
    --     16  7 20 21
    --     29 12 28 17
    --      1 15 23 26
    --      5 18 31 10
    --      2  8 24 14
    --     32 27  3  9
    --     19 13 30  6
    --     22 11  4 25
    --     ---------------------------

    val :=  din(25) & din(4 ) & din(11) & din(22) &
            din(6 ) & din(30) & din(13) & din(19) &
            din(9 ) & din(3 ) & din(27) & din(32) &
            din(14) & din(24) & din(8 ) & din(2 ) &
            din(10) & din(31) & din(18) & din(5 ) &
            din(26) & din(23) & din(15) & din(1 ) &
            din(17) & din(28) & din(12) & din(29) &
            din(21) & din(20) & din(7 ) & din(16) ;

    return val;
  end DESpbox;

  ------------------------------------------------------------------------
  -- Key left shift: left shifts the key "din" by the amount "n"
  ------------------------------------------------------------------------

  function DESkeyLshift (
    din : std_logic_vector (55 downto 0) ;
    n   : std_logic_vector ( 4 downto 0) )
  return std_logic_vector is

    variable val    : std_logic_vector (55 downto 0);

  begin
    case n is
        when "00000" =>  val := din(55 downto 28) & din(27 downto  0) ;

        when "00001" =>  val := din(54 downto 28) & din (55) &
            din(26 downto  0) & din (27) ;

        when "00010" =>  val := din(53 downto 28) & din (55 downto 54) &
            din(25 downto  0) & din (27 downto 26) ;

        when others  =>  val := din ;
    end case;

    return val;
  end DESkeyLshift;

  ------------------------------------------------------------------------
  -- Key right shift: right shifts the key "din" by the amount "n"
  ------------------------------------------------------------------------

  function DESkeyRshift (
    din : std_logic_vector (55 downto 0) ;
    n   : std_logic_vector ( 4 downto 0) )
  return std_logic_vector is

    variable val    : std_logic_vector (55 downto 0);

  begin
    case n is
        when "00000" =>  val := din(55 downto 28) & din(27 downto  0);

        when "00001" =>  val := din (28) & din(55 downto 29) & din (0) &
            din(27 downto  1) ;

        when "00010" =>  val := din (29 downto 28) & din(55 downto 30) &
            din(1 downto 0) & din(27 downto 2) ;

        when others  =>  val := din;
    end case;

    return val;
  end DESkeyRshift;

 end DESlib;

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