unit Des;

interface

uses SysUtils;

type
  TKeyByte = array[0..5] of Byte;
  TDesMode = (dmEncry, dmDecry);

  function EncryStr(Str, Key: String): String;
  function DecryStr(Str, Key: String): String;
  function EncryStrHex(Str, Key: String): String;
  function DecryStrHex(StrHex, Key: String): String;

const
  BitIP: array[0..63] of Byte =
    (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,
     56, 48, 40, 32, 24, 16,  8,  0,
     58, 50, 42, 34, 26, 18, 10,  2,
     60, 52, 44, 36, 28, 20, 12,  4,
     62, 54, 46, 38, 30, 22, 14,  6 );

  BitCP: array[0..63] of Byte =
    ( 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,
      32,  0, 40,  8, 48, 16, 56, 24 );

  BitExp: array[0..47] of Integer =
    ( 31, 0, 1, 2, 3, 4, 3, 4, 5, 6, 7, 8, 7, 8, 9,10,
      11,12,11,12,13,14,15,16,15,16,17,18,19,20,19,20,
      21,22,23,24,23,24,25,26,27,28,27,28,29,30,31,0  );

  BitPM: array[0..31] of Byte =
    ( 15, 6,19,20,28,11,27,16, 0,14,22,25, 4,17,30, 9,
       1, 7,23,13,31,26, 2, 8,18,12,29, 5,21,10, 3,24 );

  sBox: array[0..7] of array[0..63] of Byte =
    ( ( 14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
         0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
         4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
        15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13 ),

      ( 15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
         3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
         0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
        13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9 ),

      ( 10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
        13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
        13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
         1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12 ),

      (  7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
        13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
        10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
         3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14 ),

      (  2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
        14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
         4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
        11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3 ),

      ( 12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
        10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
         9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
         4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13 ),

      (  4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
        13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
         1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
         6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12 ),

      ( 13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
         1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
         7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
         2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11 ) );

  BitPMC1: array[0..55] of Byte =
    ( 56, 48, 40, 32, 24, 16,  8,
       0, 57, 49, 41, 33, 25, 17,
       9,  1, 58, 50, 42, 34, 26,
      18, 10,  2, 59, 51, 43, 35,
      62, 54, 46, 38, 30, 22, 14,
       6, 61, 53, 45, 37, 29, 21,
      13,  5, 60, 52, 44, 36, 28,
      20, 12,  4, 27, 19, 11,  3 );

  BitPMC2: array[0..47] of Byte =
    ( 13, 16, 10, 23,  0,  4,
       2, 27, 14,  5, 20,  9,
      22, 18, 11,  3, 25,  7,
      15,  6, 26, 19, 12,  1,
      40, 51, 30, 36, 46, 54,
      29, 39, 50, 44, 32, 47,
      43, 48, 38, 55, 33, 52,
      45, 41, 49, 35, 28, 31 );

var
  subKey: array[0..15] of TKeyByte;
      
implementation

procedure initPermutation(var inData: array of Byte);
var
  newData: array[0..7] of Byte;
  i: Integer;
begin
  FillChar(newData, 8, 0);
  for i := 0 to 63 do
    if (inData[BitIP[i] shr 3] and (1 shl (7- (BitIP[i] and $07)))) <> 0 then
      newData[i shr 3] := newData[i shr 3] or (1 shl (7-(i and $07)));
  for i := 0 to 7 do inData[i] := newData[i];
end;

procedure conversePermutation(var inData: array of Byte);
var
  newData: array[0..7] of Byte;
  i: Integer;
begin
  FillChar(newData, 8, 0);
  for i := 0 to 63 do
    if (inData[BitCP[i] shr 3] and (1 shl (7-(BitCP[i] and $07)))) <> 0 then
      newData[i shr 3] := newData[i shr 3] or (1 shl (7-(i and $07)));
  for i := 0 to 7 do inData[i] := newData[i];
end;

procedure expand(inData: array of Byte; var outData: array of Byte);
var
  i: Integer;
begin
  FillChar(outData, 6, 0);
  for i := 0 to 47 do
    if (inData[BitExp[i] shr 3] and (1 shl (7-(BitExp[i] and $07)))) <> 0 then
      outData[i shr 3] := outData[i shr 3] or (1 shl (7-(i and $07)));
end;

procedure permutation(var inData: array of Byte);
var
  newData: array[0..3] of Byte;
  i: Integer;
begin
  FillChar(newData, 4, 0);
  for i := 0 to 31 do
    if (inData[BitPM[i] shr 3] and (1 shl (7-(BitPM[i] and $07)))) <> 0 then
      newData[i shr 3] := newData[i shr 3] or (1 shl (7-(i and $07)));
  for i := 0 to 3 do inData[i] := newData[i];
end;

function si(s,inByte: Byte): Byte;
var
  c: Byte;
begin
  c := (inByte and $20) or ((inByte and $1e) shr 1) or
    ((inByte and $01) shl 4);
  Result := (sBox[s][c] and $0f);
end;

procedure permutationChoose1(inData: array of Byte;
  var outData: array of Byte);
var
  i: Integer;
begin
  FillChar(outData, 7, 0);
  for i := 0 to 55 do
    if (inData[BitPMC1[i] shr 3] and (1 shl (7-(BitPMC1[i] and $07)))) <> 0 then
      outData[i shr 3] := outData[i shr 3] or (1 shl (7-(i and $07)));
end;

procedure permutationChoose2(inData: array of Byte;
  var outData: array of Byte);
var
  i: Integer;
begin
  FillChar(outData, 6, 0);
  for i := 0 to 47 do
    if (inData[BitPMC2[i] shr 3] and (1 shl (7-(BitPMC2[i] and $07)))) <> 0 then
      outData[i shr 3] := outData[i shr 3] or (1 shl (7-(i and $07)));
end;

procedure cycleMove(var inData: array of Byte; bitMove: Byte);
var
  i: Integer;
begin
  for i := 0 to bitMove - 1 do
  begin
    inData[0] := (inData[0] shl 1) or (inData[1] shr 7);
    inData[1] := (inData[1] shl 1) or (inData[2] shr 7);
    inData[2] := (inData[2] shl 1) or (inData[3] shr 7);
    inData[3] := (inData[3] shl 1) or ((inData[0] and $10) shr 4);
    inData[0] := (inData[0] and $0f);
  end;
end;

procedure makeKey(inKey: array of Byte; var outKey: array of TKeyByte);
const
  bitDisplace: array[0..15] of Byte =
    ( 1,1,2,2, 2,2,2,2, 1,2,2,2, 2,2,2,1 );
var
  outData56: array[0..6] of Byte;
  key28l: array[0..3] of Byte;
  key28r: array[0..3] of Byte;
  key56o: array[0..6] of Byte;
  i: Integer;
begin
  permutationChoose1(inKey, outData56);

  key28l[0] := outData56[0] shr 4;
  key28l[1] := (outData56[0] shl 4) or (outData56[1] shr 4);
  key28l[2] := (outData56[1] shl 4) or (outData56[2] shr 4);
  key28l[3] := (outData56[2] shl 4) or (outData56[3] shr 4);
  key28r[0] := outData56[3] and $0f;
  key28r[1] := outData56[4];
  key28r[2] := outData56[5];
  key28r[3] := outData56[6];

  for i := 0 to 15 do
  begin
    cycleMove(key28l, bitDisplace[i]);
    cycleMove(key28r, bitDisplace[i]);
    key56o[0] := (key28l[0] shl 4) or (key28l[1] shr 4);
    key56o[1] := (key28l[1] shl 4) or (key28l[2] shr 4);
    key56o[2] := (key28l[2] shl 4) or (key28l[3] shr 4);
    key56o[3] := (key28l[3] shl 4) or (key28r[0]);
    key56o[4] := key28r[1];
    key56o[5] := key28r[2];
    key56o[6] := key28r[3];
    permutationChoose2(key56o, outKey[i]);
  end;
end;

procedure encry(inData, subKey: array of Byte;
   var outData: array of Byte);
var
  outBuf: array[0..5] of Byte;
  buf: array[0..7] of Byte;
  i: Integer;
begin
  expand(inData, outBuf);
  for i := 0 to 5 do outBuf[i] := outBuf[i] xor subKey[i];
                                                // outBuf       xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
  buf[0] := outBuf[0] shr 2;                                  //xxxxxx -> 2
  buf[1] := ((outBuf[0] and $03) shl 4) or (outBuf[1] shr 4); // 4 <- xx xxxx -> 4
  buf[2] := ((outBuf[1] and $0f) shl 2) or (outBuf[2] shr 6); //        2 <- xxxx xx -> 6
  buf[3] := outBuf[2] and $3f;                                //                    xxxxxx
  buf[4] := outBuf[3] shr 2;                                  //                           xxxxxx
  buf[5] := ((outBuf[3] and $03) shl 4) or (outBuf[4] shr 4); //                                 xx xxxx
  buf[6] := ((outBuf[4] and $0f) shl 2) or (outBuf[5] shr 6); //                                        xxxx xx
  buf[7] := outBuf[5] and $3f;                                //                                               xxxxxx
  for i := 0 to 7 do buf[i] := si(i, buf[i]);
  for i := 0 to 3 do outBuf[i] := (buf[i*2] shl 4) or buf[i*2+1];
  permutation(outBuf);
  for i := 0 to 3 do outData[i] := outBuf[i];
end;

procedure desData(desMode: TDesMode;
  inData: array of Byte; var outData: array of Byte);
// inData, outData 都為8Bytes，否則出錯
var
  i, j: Integer;
  temp, buf: array[0..3] of Byte;
begin
  for i := 0 to 7 do outData[i] := inData[i];
  initPermutation(outData);
  if desMode = dmEncry then
  begin
    for i := 0 to 15 do
    begin
      for j := 0 to 3 do temp[j] := outData[j];                 //temp = Ln
      for j := 0 to 3 do outData[j] := outData[j + 4];	        //Ln+1 = Rn
      encry(outData, subKey[i], buf);                           //Rn ==Kn==> buf
      for j := 0 to 3 do outData[j + 4] := temp[j] xor buf[j];  //Rn+1 = Ln^buf
    end;

    for j := 0 to 3 do temp[j] := outData[j + 4];
    for j := 0 to 3 do outData[j + 4] := outData[j];
    for j := 0 to 3 do outData[j] := temp[j];
  end
  else if desMode = dmDecry then
  begin
    for i := 15 downto 0 do
    begin
      for j := 0 to 3 do temp[j] := outData[j];
      for j := 0 to 3 do outData[j] := outData[j + 4];
      encry(outData, subKey[i], buf);
      for j := 0 to 3 do outData[j + 4] := temp[j] xor buf[j];
    end;
    for j := 0 to 3 do temp[j] := outData[j + 4];
    for j := 0 to 3 do outData[j + 4] := outData[j];
    for j := 0 to 3 do outData[j] := temp[j];
  end;
  conversePermutation(outData);
end;

//////////////////////////////////////////////////////////////

function EncryStr(Str, Key: String): String;
var
  StrByte, OutByte, KeyByte: array[0..7] of Byte;
  StrResult: String;
  I, J: Integer;
begin
  if (Length(Str) > 0) and (Ord(Str[Length(Str)]) = 0) then
    raise Exception.Create('Error: the last char is NULL char.');
  if Length(Key) < 8 then
    while Length(Key) < 8 do Key := Key + Chr(0);
  while Length(Str) mod 8 <> 0 do Str := Str + Chr(0);

  for J := 0 to 7 do KeyByte[J] := Ord(Key[J + 1]);
  makeKey(keyByte, subKey);

  StrResult := '';

  for I := 0 to Length(Str) div 8 - 1 do
  begin
    for J := 0 to 7 do
      StrByte[J] := Ord(Str[I * 8 + J + 1]);
    desData(dmEncry, StrByte, OutByte);
    for J := 0 to 7 do
      StrResult := StrResult + Chr(OutByte[J]);
  end;

  Result := StrResult;
end;

function DecryStr(Str, Key: String): String;
var
  StrByte, OutByte, KeyByte: array[0..7] of Byte;
  StrResult: String;
  I, J: Integer;
begin
  if Length(Key) < 8 then
    while Length(Key) < 8 do Key := Key + Chr(0);

  for J := 0 to 7 do KeyByte[J] := Ord(Key[J + 1]);
  makeKey(keyByte, subKey);

  StrResult := '';

  for I := 0 to Length(Str) div 8 - 1 do
  begin
    for J := 0 to 7 do StrByte[J] := Ord(Str[I * 8 + J + 1]);
    desData(dmDecry, StrByte, OutByte);
    for J := 0 to 7 do
      StrResult := StrResult + Chr(OutByte[J]);
  end;
  while (Length(StrResult) > 0) and
    (Ord(StrResult[Length(StrResult)]) = 0) do
    Delete(StrResult, Length(StrResult), 1);
  Result := StrResult;
end;

///////////////////////////////////////////////////////////

function EncryStrHex(Str, Key: String): String;
var
  StrResult, TempResult, Temp: String;
  I: Integer;
begin
  TempResult := EncryStr(Str, Key);
  StrResult := '';
  for I := 0 to Length(TempResult) - 1 do
  begin
    Temp := Format('%x', [Ord(TempResult[I + 1])]);
    if Length(Temp) = 1 then Temp := '0' + Temp;
    StrResult := StrResult + Temp;
  end;
  Result := StrResult;
end;

function DecryStrHex(StrHex, Key: String): String;
  function HexToInt(Hex: String): Integer;
  var
    I, Res: Integer;
    ch: Char;
  begin
    Res := 0;
    for I := 0 to Length(Hex) - 1 do
    begin
      ch := Hex[I + 1];
      if (ch >= '0') and (ch <= '9') then
        Res := Res * 16 + Ord(ch) - Ord('0')
      else if (ch >= 'A') and (ch <= 'F') then
        Res := Res * 16 + Ord(ch) - Ord('A') + 10
      else if (ch >= 'a') and (ch <= 'f') then
        Res := Res * 16 + Ord(ch) - Ord('a') + 10
      else raise Exception.Create('Error: not a Hex String');
    end;
    Result := Res;
  end;

var
  Str, Temp: String;
  I: Integer;
begin
  Str := '';
  for I := 0 to Length(StrHex) div 2 - 1 do
  begin
    Temp := Copy(StrHex, I * 2 + 1, 2);
    Str := Str + Chr(HexToInt(Temp));
  end;
  Result := DecryStr(Str, Key);
end;

end.