Let's say I have designed s very important system, and this system costs thousands dollars. I want to protect my system with a serial number as I know crackers will try to edit the binary code to bypass the serial number.
I have read about using a checksum function and apply it over my binary code and check the value if changed, but again, we are talking about a condition a cracker can avoid by editing the code.
My question is: what's the most used technique to protect important programs?
Don't sell your program. Keep it locked deep within your vault and never everr let anybody see it. Don't forget to wrap it in tinfoil so crackers can not use their psychic power to steal it anyway.
I have yet to see a "protected" digital product that had not been cracked pretty quickly after its publication (or in some cases, before its publication). Sorry, but it's the reality. You have to get the revenue by making a good product. Most of those who want to use it and can afford, will pay.
There will be a few dickheads, but that's life. You better be kind towards the legit users of your software and not bully them with weird copy protection attempts that don't work anyway.
The most used technique is serial numbers. But your customers will have access to the code, so they will be able to bypass your serial number check, no matter how much work you put into obfuscating it.
However, if you can provide your software as a subscription-based or one-time-payment web application, then people will not be able to do this. Whether this is feasible or not depends on the type of application you're writing.
If your app is working offline, whatever checks you do (check sums, serial code validity, etc), do them often, repeating verification code, in many routines of your software. Obfuscate your code, to make reverse engineering a more difficult task, and, if you have the possibility, implement an online check, part of the core functionality of your app residing on your server, and being serviced only to those installations that you have checked server-side for valid license key. Associate the license key to some form of unique identifier of the hardware the app is running on, and if you check online, have statistics concerning the IPs that make the verification request: if you encounter more IPs trying to verify the same license key, contact the buyer and approve a list of IPs they usually log on from, whilst blacklisting any other until specific request from them, either by mail or by phone.
Thanks for people who trying to help me
My idea is :
there are no full protected program (I am talking about off line programs)
but, you have to protect your program from the beginner crackers
protection will depend on serials and check sum and other algorithms
thanks for discussing this problem ...