Close W32Dasm, we don't need it anymore. Run OllyDBG and click on file, open, browse to our crackme and open it. Cool, you should see the asm code now.
Press F9 button from your keyboard then the crackme should show up. Enter your name and any serial number but don't click on 'check serial' button yet. This button is indicated in the picture below: picture5: On the blank box enter the first address we did found on w32dasm, DF then click ok!
Go to the second address to and set a breakpoint there too by pressing F2. See the picture below to see my breakpoints. The addresses highlighted with white means that there is set a breakpoint. So, to remove such a possibility, we can include some meaningless extra code in your source code so that a reverse engineer cannot easily break the software and this is all about the obfuscation. How to reverse engineer. In here, we are taking a keygen.
And, if you get matched with the correct details, you crack the EXE otherwise — nice try! As you can see in the above image, the details are wrong and that is why the wrong password message gets printed. Now, what we are going to do is that we will simply try to surpass this whole wrong password thing to — Right Password with the help of OllyDbg.
Emphasis on binary code analysis makes it particularly useful in cases where source is unavailable. We will upload this EXE in OllyDbg, then we will debug this file so that we get the source code where we can analyze the code with the help of the right jump conventions in the assembly language.
We will find those jumps and make them non-operational, that will simply surpass the matching details and print the right password message. Figure 2 OllyDbg. As you can see, the EXE file is loaded in the software. The source code you see is X86 assembly language and might be messy if you work it for the first time. Below, I have shown the reference architecture of X86 registers which are quite useful while dealing with assembly language. To understand in an efficient way, try this link: x86 Instruction Set.
Go to the second address to and set a breakpoint there too by pressing F2. See the picture below to see my breakpoints. The addresses highlighted with white means that there is set a breakpoint. The first breakpoint was for the name we have entered and the second is for the serial number.
Now trace line by line slowly with F8 button until you are on the address 'F' picture7: Refering to the picture too, you must be on this line: F CMP EAX, EBX Let's explain what does this mean, CMP means compare, eax register is storing the fake serial we did enter and ebx register is storing the real serial number for the entered name.
Check this on the top-right of your screen, in the above picture are number 2 and 3. Yes it is, we did found a real serial number and we can find a serial for any name we enter by following the procedure of this tutorial.
As you see, on the address. Post navigation Easy Converter 3.
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