Tweet
A simple example of how to create a time-limited evaluation program (for example 15 days). It is not affected by leap years, the number of days in a month or any other tripe.
It works simply by converting the current date to a Julian date (ie. 06-10-2008 to 2454628), adds %NumDays (ie. 15) to that to become 2454643, and stores that in the registry. Whenever the program is run it checks to see if the current Julian date is greater than the registry stored one, and if it is you know the program has expired.
A quick note on cracking ...
I kept this example as minimal as possible - it obviously provides very little security against crackers. A cracker could simply release a program (or .reg file) to delete the HKLM\Software\Test\30 Day Limit Test\ExpDate key, resetting the evaluation back to day 1.
The reason it's so easy is obviously because my example uses a static key. To make that harder for them you could use hashes of things that are at least somewhat unique to their machine, so as to create a dynamic key name. For example, the Windows directory location, or their username, or hardware 'signatures' such as their CPU ID.
It works simply by converting the current date to a Julian date (ie. 06-10-2008 to 2454628), adds %NumDays (ie. 15) to that to become 2454643, and stores that in the registry. Whenever the program is run it checks to see if the current Julian date is greater than the registry stored one, and if it is you know the program has expired.
Code:
#COMPILE EXE
#INCLUDE "win32api.inc"
'// Config ...
$sKEY = "Software\Test\30 Day Limit Test"
$sVAL = "ExpDate"
%hKEY = %HKEY_LOCAL_MACHINE
%NumDays = 15
FUNCTION reg32CreateKey(BYVAL Hive AS LONG, szKey AS ASCIIZ) AS LONG
LOCAL hKey AS LONG, Result AS LONG
IF RegCreateKeyEx(BYVAL Hive, szKey, BYVAL 0, "", %REG_OPTION_NON_VOLATILE, _
%KEY_ALL_ACCESS, BYVAL %NULL, hKey, Result) = %ERROR_SUCCESS THEN FUNCTION = 1
END FUNCTION
FUNCTION reg32SetValueDword(BYVAL Hive AS LONG, szKey AS ASCIIZ, szValue AS ASCIIZ, BYVAL dwData AS DWORD) AS LONG
DIM lRet AS LONG, hKey AS LONG
lRet = RegOpenKeyEx(Hive, szKey , 0&, %KEY_ALL_ACCESS, hKey)
IF lRet = %ERROR_FILE_NOT_FOUND THEN
lRet = reg32CreateKey(BYVAL Hive, szKey)
IF lRet = 0 THEN EXIT FUNCTION
CALL RegOpenKeyEx(Hive, szKey, 0&, %KEY_ALL_ACCESS, hKey)
IF hKey = 0 THEN EXIT FUNCTION
END IF
lRet = RegSetValueEx(hKey, szValue, 0&, %REG_DWORD, dwData, BYVAL 4)
RegCloseKey hKey: IF lRet = 0 THEN FUNCTION = 1
END FUNCTION
FUNCTION reg32GetValueDword(BYVAL Hive AS LONG, szKey AS ASCIIZ, szValue AS ASCIIZ) AS DWORD
ON ERROR RESUME NEXT
LOCAL dwBuf AS DWORD, hKey AS LONG
IF RegOpenKeyEx(Hive, szKey, 0&, %KEY_ALL_ACCESS, hKey) = %ERROR_SUCCESS THEN
CALL RegQueryValueEx(BYVAL hKey, szValue, BYVAL 0, %REG_DWORD, BYVAL VARPTR(dwBuf), 4)
RegCloseKey hKey
FUNCTION = dwBuf
END IF
END FUNCTION
FUNCTION Date2Julian(MM_DD_YYYY AS STRING) AS LONG '// by Mike Doty
DIM Month&,Day&,Year&
Month = VAL(LEFT$(MM_DD_YYYY$,2))
Day = VAL(MID$(MM_DD_YYYY$,4,2))
Year = VAL (RIGHT$(MM_DD_YYYY$,4))
LOCAL k AS LONG, Julian AS LONG
k = INT((14 - Month) / 12)
Julian = Day + INT(367 * (Month + (k * 12) - 2) / 12) _
+ INT(1461 * (Year + 4800 - k) / 4) - 32113
Julian = Julian - (INT(3 * INT((Year + 100 - k) / 100) / 4) - 2) 'Convert to Gregorian
Date2Julian = Julian
END FUNCTION
'################################################################################################################
FUNCTION PBMAIN() AS LONG
LOCAL dwCurDay AS LONG, dwDays AS LONG, dwDaysLeft AS LONG
dwCurDay = Date2Julian(DATE$)
dwDays = reg32GetValueDword(BYVAL %hKEY, $sKEY, $sVAL)
IF dwDays = 0 THEN '// NEW INSTALLATION
dwDays = dwCurDay + %NumDays
reg32SetValueDword(BYVAL %hKEY, $sKEY, $sVAL, BYVAL dwDays)
STDOUT "Installed"
ELSE '// ALREADY BEEN INSTALLED
dwDaysLeft = dwDays - dwCurDay
IF dwDaysLeft > %NumDays THEN
STDOUT "Cracker warning, number of days left is greater than the evaluation period"
ELSEIF dwDaysLeft =< 0 THEN
STDOUT "EXPIRED"
ELSE
STDOUT "Days left = " & STR$(dwDaysLeft)
END IF
END IF
WAITKEY$
END FUNCTION
I kept this example as minimal as possible - it obviously provides very little security against crackers. A cracker could simply release a program (or .reg file) to delete the HKLM\Software\Test\30 Day Limit Test\ExpDate key, resetting the evaluation back to day 1.
The reason it's so easy is obviously because my example uses a static key. To make that harder for them you could use hashes of things that are at least somewhat unique to their machine, so as to create a dynamic key name. For example, the Windows directory location, or their username, or hardware 'signatures' such as their CPU ID.
Comment