Reducing piracy of iPhone applications

UPDATE

Please visit and read

Thanks to chpwn in the comments.

Code that's way too old! - 11th May 2009

For now there's an easier way to detect if your iPhone application has been cracked for piracy use. This does not involve you to check the iPhone unique IDs against a list of accepted IDs.

Currently there are three things crackers do:

1. Edit the Info.plist file
2. Decode the Info.plist from binary to UTF-8 or ASCII
3. Add a key-pair to Info.plist{SignerIdentity, Apple iPhone OS Application Signing}

The last one is easiest to check with this code:

NSBundle *bundle = [NSBundle mainBundle]; 
NSDictionary *info = [bundle infoDictionary]; 
if ([info objectForKey: @"SignerIdentity"] != nil) 
{ /* do something */  }

Generally we don't have SignerIdentity in any of the App Store applications we build so checking for nil then performing set instructions should make it more difficult for crackers and pirates.

I can't take credit for this so please visit How to Thwart iPhone IPA Crackers. There's loads of information there about piracy on iPhone and how to curb it.

As pointed out by Andrey Tarantsov in the comments, looking for the "SignerIdentity" string in the binary (using an app like HexEdit) and replacing it is pretty easy.

You could encode that string, but then again all you have to do is change one char of it and the app is not going to look for the "SignerIdentity" key anymore but for some other key that probably doesn't exist (therefore is null). That key being null, the app thinks it isn't cracked (since SignerIdentity should be null if the app isn't cracked).

Instead, I'd rather check the size of the info.plist and compare it to a reference value. I noticed Simulator and Devices builds don't have the same info.plist file size. Same goes for Debug, Release and Distribution builds. Therefore, make sure you set the reference value using the info.plist file size for the Device Distribution Build.

How to look for the filesize at launch: