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Author Topic: How to remove CRC check from a exe?  (Read 5655 times)

megatron

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How to remove CRC check from a exe?
« on: January 02, 2009, 03:12:49 PM »
Anyone has some tips to remove CRC check from exe.

I have a exe which has is_debug_present and some assembly which I had to change. But now when I run that program I get some error “error unpacking program”. I think the exe has some internal CRC check.

Problems while remove CRC:
1. I think the error string shown is generated at runtime, so I cannot find from memory map and put BP
2. I cannot see any references to show window, msgbox etc.

Anyone can provide some tips to fight these anti-reverse eng ticks.

I am using the latest ollydbg-200i, which has very good support for putting memory point anywhere (old ollydbg gives problem if I put breakpoint in some memory areas)

mouser

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Re: How to remove CRC check from a exe?
« Reply #1 on: January 02, 2009, 03:35:20 PM »
if this is related to removing a license protection on a program, that's just not something that we permit discussing on this forum, sorry.

Ehtyar

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Re: How to remove CRC check from a exe?
« Reply #2 on: January 02, 2009, 03:35:31 PM »
megatron, you'll need to explain what it is you're trying to accomplish in more detail so that we can determine you're not engaging in piracy before we help you. Be as forthcoming as you possibly can.

Ehtyar.

megatron

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Re: How to remove CRC check from a exe?
« Reply #3 on: January 02, 2009, 03:55:30 PM »
Definitely I am going to remove a license from a program for piracy or to use it illegally. I want to figure out how it is done, so that I can also use the same. And put some more protection over it instead of using some packer program like ASProtect (which I think is already broken)

scancode

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Re: How to remove CRC check from a exe?
« Reply #4 on: January 02, 2009, 03:59:44 PM »
Definitely I am going to remove a license from a program for piracy or to use it illegally.

Aren't you missing a "NOT" there?

megatron

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Re: How to remove CRC check from a exe?
« Reply #5 on: January 02, 2009, 04:04:53 PM »
I am sorry, typo error… missed “NOT”  :D

f0dder

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Re: How to remove CRC check from a exe?
« Reply #6 on: January 02, 2009, 05:04:39 PM »
You're probably a lot better off heading over to the RCE Forums - they deal specifically with reverse engineering and software (de)protection. I'm sorry to say it, but the way you phrased the original post sounds a bit suspicious to me, and I'm not sure this kind of discussion fits well here at DC anyway?
- carpe noctem

scancode

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Re: How to remove CRC check from a exe?
« Reply #7 on: January 02, 2009, 05:06:54 PM »
I'm sorry to say it, but the way you phrased the original post sounds a bit suspicious to me, and I'm not sure this kind of discussion fits well here at DC anyway?

Commercial software unpacking/unwraping. Definitely cody-unfriendly stuff.
Mods, take good care of this thread.

app103

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Re: How to remove CRC check from a exe?
« Reply #8 on: January 02, 2009, 05:15:44 PM »
Ok, I am going to lock this thread and if mouser thinks it's appropriate, he can unlock it.