How to encrypt or obfuscate objective c code? [duplicate]

Question

Possible Duplicate:
iPhone/iPad App Code Obfuscation - Is it Possible? Worth it?

I have spent a lot of time on this and I couldn't able to find a perfect answer. That's why I decided to put my question here. I have an iPhone application and want to encrypt the code to prevent from class-dump or otool utilities. (Tools used to dump out the headers from executable). I would like to know is there any way to encrypt the source code or obfuscate the source code?

Answer 1

It's a lot more complicated than it might seem initially. Any tool that mangles method names has the potential to fudge up:

1. KVC compliance
2. The use of dynamically generated selectors
3. Nib file compatibility
4. Protocol conformance
5. Method inheritance

Obfuscation is just another layer to deal with; often obfuscation is easily reversed. It is not really possible to “encrypt” your classes because the Objective-C runtime and Cocoa framework won't know how to decrypt it. Anyone determined enough will eventually figure out how your program works.

Answer 2

Actually you can provide some obfuscation and tamper protection with specialist 3rd party tools. There are 2 companies, I know of, that provide tools or services to do this : Arxan and irDato.

Neither are cheap or accessible to small developers but if you are developing for a large corporation then you should consider them.

Obfuscation is done by mangling code paths and adding redundant instructions so as to confuse anybody trying to reverse engineer the code. Tamper protection is done by adding checksums to the code and embedding checksum checks within functions. You can create a network of interdependent checksums that makes it extremely difficult to bypass them. There are a few other things that can be done but you really need to talk to specialists in this area.

Further to the earlier answer, Apple does not encrypt the binaries but just signs them. It is fairly easy to reverse engineer and modify app binaries on a jailbroken device.