How to make keygen for JubeCrackme

Version 1.0 by Jube

Written by tnHuAn

Well, as I say in the last tutorial , in this tutorial , I will show you : How to make a keygen for Jube Crackme1. This Crackme is very is, and I think it is a very good example for newbie try to make a keygen.To make keygen for this crackme, all you need is a simple XOR. 

NOTE: this crackme only working in win9x, so you must run it in Win9x , or You can't run it.

Now, let's do....

• SoftIce ( I used version 4.05 for Win9X ).
• A paper and a pen.
• Some music form Andy Law CD ( I like his song, it's very good ).
• Visual Basic 6.0 for code the keygen.

You can find all tool at : http://crackpltools.prv.pl and at your home.

    http://crackmes.prv.pl

Essay

First, You must run this crackme, and you will see 2 textbox, you must enter your name and find the correct serial. Now I enter my name , and fake serial as :

• Name: tnhuan
• Serial: 123456789

Don't click OK button, press Ctrl+D, to pop up SoftIce, get a breakpoint at GetWindowtextA, so type :     bpx GetWindowTextA, press Enter. Then press F12 , until you are in this crackme code, press F10 to trace over the code. Keep pressing F10 until you see this code :

• Cmp    DWORD PTR [004021C6], 01
• Jnz       004011D7
• Xor      Eax, 007BF
• Mov     [004021BA], Eax (1)

Look, at the line : Xor Eax, 007BF , type in SoftIce : ? Eax, you will see : Eax=123456789, and this is my fake serial. Ok, it get my fake serial, then XOR it with 007BF ( =1983 ). Well, continue trace the code, until you see this code :

• Call    User32!GetWindowTextA
• Mov   Ecx, 004021CA <--- Eax contain my name
• Xor    Eax, Eax <---Clear Eax
• Xor    Ebx, Ebx <---Clear Ebx
• Mov   Bl, [ Ecx] <---Get Hex value of every character in my name
• Cmp   Bl, 00   <---Compare it with 00
• Jnz      00401165 <----if not, jump...
• Add    Eax, Ebx <--- Eax=Eax+Ebx
• Inc      Ecx <--- Ecx=Ecx+1
• Jmp    004115C <--- Jmp to 004115C
• Xor    Eax, 007D0 
• Cmp   [004021BA], Eax (2)

OK, look at this part of code, this is a loop, and this loop will get hex value in every character in my name, then add all of value. Ex : my name : tnhuan, then : Eax =  116+110+104+117+97+110=654. Then it XOR this result with 7D0 ( = 2000 ). And I will register if (1)=(2).

Now, I will calculate my serial :

• 654 Xor 2000=1374
• 1374 Xor 1983= 737

And my correct serial is : 737, hey the calculation very simple, all you need is : XOR.

Here is my keygen source code , I code it in Visual Basic.

Private Sub Command1_Click()
    Dim Dodai As Integer
    Dodai = Len(Text1.Text)
    If Dodai < 4 Then MsgBox ("Length of name must >= 4")
    Dim i As Integer
    Dim Char As String
    Dim Ten As String, Hang As Integer
    Dim A As Integer, B As Integer
    B = 0
    Ten = Text1.Text
    For i = 1 To Dodai
        Char = Mid(Ten, i, 1)
        A = Asc(Char)
        B = B + A
    Next i
    B = B Xor 2000
    B = B Xor 1983
    Text2.Text = B
End Sub

Well , I hope you will make this keygen by yourseft... That is all ..... 

If you want to comment me anything about this tutorial , please email to me :

    tnhuan19@hotmail.com