How to create the 30-day limit on eval program?

Great Ones,

I'm writing a demo version of a program I'm intending to ultimately sell...but I want the demo version to only operate for 30-days.

What is the best way to go about programming such a 30-day lock?

Thank you in advance,
Jeff

You could create a log in the registry saying what the install date was and what the date is now, therefore in 30 days exiting immediately. However, they could set it to be a day before that to overcome it. You'd probably have to do some kind of counter to get it to work properly.

Sastraxi,

Your idea sounds great. I would just 'encrypt' (with some sort of simle formula) the two dates, making it harder for them to trivially 'hack' the dates. But how do you register and read/write into the registry from VB. Do you have an example or know where I could look in MSDN for example?

Thank you

VB Code:

'Author: Reginald Wheat 
 
Option Explicit
 
Public Function DateGood(NumDays As Integer) As Boolean
    'The purpose of this module is to allow you to place a time
    'limit on the unregistered use of your shareware application.
    'This module can not be defeated by rolling back the system clock.
    'Simply call the DateGood function when your application is first
    'loading, passing it the number of days it can be used without
    'registering.
    '
    'Ex: If DateGood(30)=False Then
    ' CrippleApplication
    ' End if
    'Register Parameters:
    ' CRD: Current Run Date
    ' LRD: Last Run Date
    ' FRD: First Run Date
 
    Dim TmpCRD As Date
    Dim TmpLRD As Date
    Dim TmpFRD As Date
 
    TmpCRD = Format(Now, "m/d/yy")
    TmpLRD = GetSetting(App.EXEName, "Param", "LRD", "1/1/2000")
    TmpFRD = GetSetting(App.EXEName, "Param", "FRD", "1/1/2000")
    DateGood = False
 
    'If this is the applications first load, write initial settings
    'to the register
    If TmpLRD = "1/1/2000" Then
        SaveSetting App.EXEName, "Param", "LRD", TmpCRD
        SaveSetting App.EXEName, "Param", "FRD", TmpCRD
    End If
    'Read LRD and FRD from register
    TmpLRD = GetSetting(App.EXEName, "Param", "LRD", "1/1/2000")
    TmpFRD = GetSetting(App.EXEName, "Param", "FRD", "1/1/2000")
 
    If TmpFRD > TmpCRD Then 'System clock rolled back
        DateGood = False
    ElseIf Now > DateAdd("d", NumDays, TmpFRD) Then 'Expiration expired
        DateGood = False
    ElseIf TmpCRD > TmpLRD Then 'Everything OK write New LRD date
        SaveSetting App.EXEName, "Param", "LRD", TmpCRD
        DateGood = True
    ElseIf TmpCRD = Format(TmpLRD, "m/d/yy") Then
        DateGood = True
    Else
        DateGood = False
    End If
End Function
 
 
'Usage 
 
 Private Sub Form_Activate()
    If Not DateGood(30) Then
        MsgBox "Trial Period Expired!", vbExclamation, "Unregistered application"
        Unload Me
    End If
End Sub

yet another sample :)

SaveSetting would be almost worse then an ini, or simple text file stored in the program Directory. Do a search for "VB" in your registry,, and you should find a folder eventually that has nothing but Registry Entires put there using SaveSetting. This location is the same in everyone's registry.

If you are going to use the registry, look up the Registry functions in MSDN, and learn to use them. Hide your settings with some strage name, in some strange place.

You might also want to create a binary file in your Windows\System32 directory, renamed to <something>.DLL. Encrypt the date so there is nothing but numbers. The first number in the file should be the length of the date, then the date, followed by several kilobytes of junk.

Z.