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DJKeyObfuscation

Helps facilitate key obfuscation.

Read the comments in the "work" function of DJKeyObfuscation.m to hopefully understand more of what this does.

Using

  1. Use the "printObfuscationSecretArray:" function to NSLog() what this array is supposed to be. Take this value and store it. This is a byte array of SHA(class name) XOR'ed with the secret key. (for obfuscation)
  2. Delete any other string reference to your secret key.
  3. When you need your key, call "keyFromArray:length:" with the stored byte array. This will convert the obfuscated byte array back into the key
  4. Use the key, then discard.

Recommended

It is recommended to also add the following to your main.m function to disable debugging attacks

#import <dlfcn.h>
#import <sys/types.h>

typedef int (*ptrace_ptr_t)(int _request, pid_t _pid, caddr_t _addr, int _data);
#if !defined(PT_DENY_ATTACH)
#define PT_DENY_ATTACH 31
#endif  // !defined(PT_DENY_ATTACH)

void disable_gdb() {
    void* handle = dlopen(0, RTLD_GLOBAL | RTLD_NOW);
    ptrace_ptr_t ptrace_ptr = dlsym(handle, "ptrace");
    ptrace_ptr(PT_DENY_ATTACH, 0, 0, 0);
    dlclose(handle);
}

int main(int argc, char *argv[]) {
    #if !(DEBUG) // Don't interfere with Xcode debugging sessions.
        disable_gdb();
    #endif

    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil,
            NSStringFromClass([MyAppDelegate class]));
    }
}

Resources

Check out http://www.splinter.com.au/2014/09/16/storing-secret-keys/ for full description of proper obfuscation.