请教一个算法问题

Question

我现在的程序，想通过验证ＣＤＫＥＹ来确定系统的用户数目和过期日期。想请教一下具体实现的思路和方法，谢谢。

Answer 1

//呵呵，以下是我自己创造的一对函数，希望可以帮的上楼主！  ^_^
//给定用户ID和客户序号产生28为CDKEY
//Length(UserLen)<=10
function GetEasyCDKEY(UserID:String;UserIndex:Integer):String;
var
  DATAStr:String;
  TS:Comp;
  i,j,CheckSum:Integer;
begin
  TS:=TimeStampToMSecs(DateTimeToTimeStamp(Now));
  DATAStr:=IntToHex(PInt64(@TS)^,12)+IntToHex(UserIndex XOR $77777777,8);
  CheckSum:=1;
  j:=1;
  for i:=1 to Length(UserID) do
  begin
    Inc(CheckSum,Ord(UserID[i])+Ord(DATAStr[j])-64);
    Inc(j);
    if j>20 then j:=1;
  end;
  Result:=DATAStr+IntToHex(CheckSum XOR $77777777,8);
end;
//检测用户和CDKEY有效性，如果检测成功返回True同时返回注册时间和用户序号.
function CheckEasyCDKEY(UserID,CDKEY:String;var regDateTime:TDateTime;var UserIndex:Integer):Boolean;
var
  DATAStr:String;
  TS:Comp;
  i,j,CheckSum:Integer;
begin
  Result:=False;
  if Length(CDKEY)<>28 then Exit;
  DATAStr:=Copy(CDKEY,1,20);
  CheckSum:=1;
  j:=1;
  for i:=1 to Length(UserID) do
  begin
    Inc(CheckSum,Ord(UserID[i])+Ord(DATAStr[j])-64);
    Inc(j);
    if j>20 then j:=1;
  end;
  try
    if CheckSum<>(StrToInt('$'+Copy(CDKEY,21,8)) XOR $77777777) then Exit;
    PInt64(@TS)^:=StrToInt64('$'+Copy(DATAStr,1,12));
    regDateTime:=TimeStampToDateTime(MSecsToTimeStamp(TS));
    UserIndex:=StrToInt('$'+Copy(DATAStr,13,8)) XOR $77777777;
  except
    on E:Exception do Exit;
  end;
  Result:=True;
end;
//测试
procedure TForm1.Button1Click(Sender: TObject);
var
  R:String;
  regdt:TDateTime;
  UserIndex:Integer;
begin
  R:=GetEasyCDKEY('quanqi',100);
  if CheckEasyCDKEY('quanqi',R,regdt,UserIndex) then
  ShowMessage(R+#13
              +DateTimeToStr(regdt)+#13
              +IntToStr(UserIndex));
end;