Sapphire String Crypter

function XorEncode(Source, Key: string): string;
var
  I : Integer;
  C : Byte;
begin
  Result := '';
    for I := 1 to Length(Source) do begin
    if Length(Key) > 0 then
      C := Byte(Key[1 + ((I - 1) mod Length(Key))]) xor Byte(Source[I])
      else
      C := Byte(Source[I]);
      Result := Result + AnsiLowerCase(IntToHex(C, 2));
  end;
end;

function XorDecode(Source, Key: string): string;
var
  I: Integer;
  C: Char;
begin
  Result := '';
  for I := 0 to Length(Source) div 2 - 1 do begin
    C := Chr(StrToIntDef('$' + Copy(Source, (I * 2) + 1, 2), Ord(' ')));
    if Length(Key) > 0 then
    C := Chr(Byte(Key[1 + (I mod Length(Key))]) xor Byte(C));
    Result := Result + C;
  end;
end;

Beispiele :

// Crypt
procedure TForm1.Button1Click(Sender: TObject);
begin
  Memo1.Text := XorEncode(Memo1.Text, '123')
end;

// Decrypt
procedure TForm1.Button2Click(Sender: TObject);
begin
   Memo1.Text := XorDecode(Memo1.Text, '123')
end;