Insomniac came out with the Spyro game 10 years ago. I played it a couple times. It has some nice animation when the little dragon flies around. The company had their profits robbed when their game was quickly cracked for the Playstation. They decided to step up their anti-crack efforts with the release of their Spyro Year of the Dragon release. They shared some of what they did to protect their program and their revenue. I highlight some of their techniques here because it is very interesting.
The first thing to realize is that no program is crack proof. You are only trying to delay crackers when you put protection in there. It is a cat and mouse game. Typical cracks insert some intro code which tell the user who cracked the game. Then the crack runs the normal executable that is cracked. The normal executable is compressed to keep the overall size of the game the same.
So how to do prevent such a crack? A simple method is to introduce checksums. You see whether the code has been altered. If it has, you do something to prevent the game from continuing. There are ways to store checksum data in tables which makes checksum anticrack methods weak. The better checksum protection interleaves the checksum protection with actual program code.
Crackers do their work in their spare time. Make it hard for them to debug your application. Then it will also be hard for them to crack your app. Another technique that works is to delay what you do on detection of the app being cracked. That way it is hard for crackers to test whether the crack worked. They may also just assume that the crack worked, when in reality you will detect the crack and later halt the game.
I put some simple encryption into a product for work once. It was just a way to encrypt keys that were required to activate the app. Luckily we did not have a lot of general users who wanted a cracked app. This was just a method to keep the business users honest. They were too busy to actually crack the darn thing. If you are selling to the general public, you are going to want to research ways of your own to slow down the crackers. Your profit may hinge on the productivity of this effort.
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