Encrypting Variables in Memory to Prevent Hacking

Previously I talked about how hackers can use memory tools to find and directly update crucial game variables on the fly. The solution to this is to encrypt those values. This means that if a hacker searches for a known value (like score) they will fail to find the right one because the score is encrypted in memory.

I felt like dabbling in Flash a bit today so I went ahead and created a little utility to make the in-memory encryption easy. It's written as a pair of AS3 classes. One of them is the TEA implementation from the ASCrypt3 library while the other is the utility itself. This type of system isn't useful if it isn't simple to use so that was the main goal. All methods are implemented as static to avoid needing to instantiate the utility. You can see pretty much every method below:

// Create a handle for the variable
var scoreName:String = "score";

// Set the initial score to 100
MemoryCrypto.setValue(scoreName, 100);

// Increment the score by 100, new value = 200
MemoryCrypto.incrementValue(scoreName, 100);

// Decrement the score by 50, new value = 150
MemoryCrypto.decrementValue(scoreName, 50);

// Multiply the score by 4, new value = 600
MemoryCrypto.multiplyValue(scoreName, 4);

// Divide the score by 2, new value = 300
MemoryCrypto.divideValue(scoreName, 2);

// Get the score
var score:Number = MemoryCrypto.getValue(scoreName);

// Display the score, 300
trace(score);

Pretty simple. Internally it creates an instance of the TEA cipher and a pair of random numbers become the key. This key is then used for all encryption. The variable values are only unencrypted long enough to change and then re-encrypted for storage.

This solution is NOT infallible. A dedicated hacker will be able to actually tear the code apart in memory as opposed to just doing value-based searches but this will make it an order of magnitude harder then otherwise. It will stop many of the script-kiddies dead in their tracks.

The code is available here and free for any use. Have fun!