For paid app only.
Two brains are better than one, three are better than two and so on.
I implement this code to protect my apps from illegal uses, crackers and hackers who try to unlock my apps functionality without paying me or my agreement.
My apps are time based, so time is very important flag in my calculation.
I decide to share it with you, to explore its weakness and increase its complexity and make it impenetrable method used by all of us in our apps.
Also to extend it to cover non-time based apps protection.
Let's start:
In manifest file editor, add this code:
Create new service, I named it applicationlocker as the following:
Usage:
What other possible tricks crackers think?
Discussion of this scenario and increasing its strength is useful for all of us and making this code anti-hacker-proven method.
Two brains are better than one, three are better than two and so on.
I implement this code to protect my apps from illegal uses, crackers and hackers who try to unlock my apps functionality without paying me or my agreement.
My apps are time based, so time is very important flag in my calculation.
I decide to share it with you, to explore its weakness and increase its complexity and make it impenetrable method used by all of us in our apps.
Also to extend it to cover non-time based apps protection.
Let's start:
In manifest file editor, add this code:
B4X:
AddReceiverText(applicationlocker,
<intent-filter>
<action android:name="android.intent.action.TIME_SET"/>
<action android:name="android.intent.action.TIMEZONE_CHANGED"/>
<action android:name="android.intent.action.TIME_CHANGED"/>
</intent-filter>
)
B4X:
#Region Service Attributes
#StartAtBoot: True
#End Region
' Libraries used: ByteConverter, JavaObject, Encryption and DateUtils
Sub Process_Globals
'These global variables will be declared once when the application starts.
'These variables can be accessed from all modules.
End Sub
Sub Service_Create
End Sub
Sub Service_Start (StartingIntent As Intent)
Service.StopAutomaticForeground 'Call this when the background task completes (if there is one)
If StartingIntent.Action="android.intent.action.TIMEZONE_CHANGED" Or StartingIntent.Action="android.intent.action.TIME_CHANGED" Or StartingIntent.Action="android.intent.action.TIME_SET" Then
File.Delete(File.DirInternal,"system")
End If
End Sub
Sub Service_Destroy
End Sub
'check app use is legal
Public Sub islegal() As Boolean
'1- check if system file exist
If (File.Exists(File.DirInternal,"system"))=False Then Return False
'2- check if file content match the file creation time - not created/copied by illegal user
Dim filecontent As String=File.ReadString(File.DirInternal,"system")
Dim filecreationtime As Long = GetCreationTime(File.DirInternal,"system")
If filecontent<>getMD5(filecreationtime) Then
File.Delete(File.DirInternal,"system")
Return False
End If
'3- check if usetime ellapsed against device datetime
Dim p As Period=DateUtils.PeriodBetween(filecreationtime,DateTime.Now)
If p.Months>=1 Then 'used time in months, you can change it according your needs
File.Delete(File.DirInternal,"system")
Return False
End If
'4- check if device datetime changed
'it will be triggered when change happen and delete "system" file in DirInternal
'see Service_Start
'5- check last/maximum transaction date in your app database if time diff larger than legal time
'write your code here .. return False if time consumed
Return True
End Sub
'should be called once - example when app purchase or subscription payment done
Public Sub createlockfile
If File.Exists(File.DirInternal,"system") Then
File.Delete(File.DirInternal,"system")
Sleep(200)
File.WriteString(File.DirInternal,"system",getMD5(GetCreationTime(File.DirInternal,"system")))
Else
File.WriteString(File.DirInternal,"system",getMD5(GetCreationTime(File.DirInternal,"system")))
End If
End Sub
'Android 26+ by @Erel
Sub GetCreationTime (Dir As String, FileName As String) As Long
Dim Files As JavaObject
Files.InitializeStatic("java.nio.file.Files")
Dim FileSystems As JavaObject
Dim FileSystem As JavaObject = FileSystems.InitializeStatic("java.nio.file.FileSystems").RunMethod("getDefault", Null)
Dim Path As JavaObject = FileSystem.RunMethod("getPath", Array(File.Combine(Dir, FileName), Array As String()))
Dim BasicFileAttributes As JavaObject
BasicFileAttributes.InitializeStatic("java.nio.file.attribute.BasicFileAttributes")
Dim LinkOptions As JavaObject
LinkOptions.InitializeArray("java.nio.file.LinkOption", Array())
Return Files.RunMethodJO("getAttribute", Array(Path, "creationTime", LinkOptions)).RunMethod("toMillis", Null)
End Sub
Sub getMD5(str As String) As String
Dim md As MessageDigest
Dim ByteCon As ByteConverter
Dim md5hash() As Byte
md5hash = md.GetMessageDigest(str.GetBytes("UTF8"),"MD5")
Dim md5string As String
md5string = ByteCon.HexFromBytes(md5hash)
Return md5string
End Sub- Call createlockfile function once when:
- Your app is paid from the beginning (in first run), so the lock file should be created
- In-app purchase or subscription success
- Check islegal function everytime you want to check the user is legal
- Note that islegal function step 3 can be modified according your need, in my example I'm assuming time period one month.
- Delete dirinternal "system" file -> the islegal function step 1 disable app use
- Clone "system" file from device to device -> the islegal function step 2 disable app use
- If allowed time consumed -> the islegal function step 3 disable app use
- Change device datetime -> Service_Start disable app use
- Clone the entire device (including our app) to another device -> that is mean everything will resumed from stopped point in previous device -> useless cracker trick
What other possible tricks crackers think?
Discussion of this scenario and increasing its strength is useful for all of us and making this code anti-hacker-proven method.
