XTEA (Encryption Algorithm)

[trifid]

Der XTEA ist ein sehr schlanker Blockziffernalgorithmus.
Dieser Algorithmus verschlüsselt 64-bit Daten-Blöcke mit einer Schlüssellänge von 128-bit.
XTEA ist keinen Patenten unterworfen.

näheres unter Wikipedia - XTEA

Das Modul xtea.pas mit der Implementierung

Delphi-Quellcode:

unit xtea;

interface

uses Classes;

{$OVERFLOWCHECKS OFF}

type TxteaKey  = array[0..3] of LongWord;
type TxteaData = array[0..1] of LongWord;

type
  Txtea = class(TPersistent)
  public
   procedure Crypt (Key : TxteaKey; var Data : TxteaData);
   procedure Decrypt (Key : TxteaKey; var Data : TxteaData);
  end;

implementation

procedure Txtea.Crypt (Key : TxteaKey; var Data : TxteaData);
   var Summe : LongWord;
   var Delta : LongWord;
   var n     : Integer;
begin
   Summe := 0;
   Delta := $9E3779B9;

   for n := 1 to 32 do
   begin
      Data[0] := Data[0] +
            ( (((Data[1] shl 4) xor (Data[1] shr 5)) + Data[1]) xor
                (Summe + Key[Summe and 3]) );
      Summe := Summe + Delta;

      Data[1] := Data[1] +
            ( (((Data[0] shl 4) xor (Data[0] shr 5)) + Data[0]) xor
                (Summe + Key[Summe shr 11 and 3]) );
   end;
end;

procedure Txtea.Decrypt (Key : TxteaKey; var Data : TxteaData);
   var Summe : LongWord;
   var Delta : LongWord;
   var n     : Integer;
begin
   Summe := $C6EF3720;
   Delta := $9E3779B9;

   for n := 1 to 32 do
   begin
      Data[1] := Data[1] -
            ( (((Data[0] shl 4) xor (Data[0] shr 5)) + Data[0]) xor
                (Summe + Key[Summe shr 11 and 3]) );
      Summe := Summe - Delta;
      Data[0] := Data[0] -
            ( (((Data[1] shl 4) xor (Data[1] shr 5)) + Data[1]) xor
                (Summe + Key[Summe and 3]) );
   end;
end;

end.

Auszug aus einem Beispiel

Delphi-Quellcode:

procedure TForm1.Button1Click(Sender: TObject);
   var xtea : Txtea;
   var Key  : TxteaKey;
   var Data : TxteaData;
begin
   xtea := Txtea.Create;
   try
      Key[0] := 9999;
      Key[1] := 8888;
      Key[2] := 7777;
      Key[3] := 6666;

      Data[0] := 1357;
      Data[1] := 2468;
      
      xtea.Crypt (Key, Data);
      xtea.Decrypt (Key, Data);
   finally
      xtea.Free;
   end;
end;