Self Deleting iPhone app

Question

I have a iPhone app which needs to have a self destruct option. This app is going to be use on sensitive locations and holds some algorithms which are not to be known by anybody except the iPod Holder.

What would be the most "complete" way of deleting the app?

I was thinking of some how writing zeros to the nib file. or the actual application.app but I believe this folders are write protected and sandboxed.

Anybody have any ideas of better ways to achieve this?

Elaboration (Taken from original poster's comments):

This is for a jailbroken iPhone.

These devices are going to be provided to military personnel this device falling into enemy hands would be the least of my concerns. It's going to have a button so wipe the app once the app is written to zero or better yet corrupted with garbage all over the "exe" the app has no way of working and it would require inspection of the iPod flash chip with equipment that i 100% know the wrong people wont have

Answer 1

I'm going to go out on a limb here and say you may not want to use the iphone for this type of app. There are intentional limitations to this exact type of action on the iphone and in springboard. If you are doing something so sensitive that it can't fall into unauthorized hands my recommendation would be to use a different and more customizable/controllable platform.

Answer 2

The folders are sandboxed, but your application is in there. On my jailbroken iPhone I see that all the permissions are owned by mobile so I don't see any reason why you can't just overwrite all the files with zeroes and then delete them.

Answer 3

The application bundle is effectively read-only, perhaps you should store some of the information in an encrypted form somewhere on a network.

Answer 4

Unless you're working from a jailbroken device, you're probably going to run into problems here.

Even if you can find a way to automatically delete the app, you're still running the risk of those algorithms getting into the wrong hands - you would essentially be running into the same problems that Apple has with jailbreaking - once the device is in someone else's hands, it only takes the proper amount of motivation for the data to be accessed.

The only way to secure your algorithms is to pass the data to a remote server and get the results. There's still a possibility of a security breach, but it's much, much lower.

Answer 5

Even if you find a way to write over the app in the flash memory, you really aren't erasing the app. Flash memory chips use wear leveling algorithms to reduce writes to the same blocks and so when you write out zeroes they are typically written to a new block of memory and not to the same block used before, so you really aren't erasing anything. The data can still be recovered from the flash chip (by a pro).

Another option is to separate out the parameters of the algorithm so that the algorithm is no longer sensitive (or at least not usable) and provide the parameters encrypted in a file. Then provide the key to authorized users via the network and don't store that key into flash, only RAM. They would need to get the key every time they start the app. Only give the key to authorized users. Of course, you'll also need to encrypt that key for transmission over the network with another key... There are systems for doing this, don't invent your own, in any case you'll need a crypto expert to do this right.

Answer 6

I don't know how well this would work, but you could store the algorithm as a file inside the application bundle, run the algorithm from that file possibly using a scripting language or something, and delete that file if you need to.

Answer 7

If you are openly storing the code that contains this algorithm within your application, there's nothing stopping the "wrong people" from jailbreaking the device and copying the complete file structure of the device before you run your "wipe" process.

Additionally, if you are dealing with a U.S. Government customer, I doubt that they will approve of the purchase of a jailbroken device, given that the vendor of such a device has claimed that jailbreaking is illegal. Whether or not this will hold up in court, the government tends to be conservative in these matters and err on the side of caution. Because Apple is a large U.S. company and a vendor to the government, I wouldn't expect the government procurers to take the jailbreakers' side in this.

My recommendation would be to encrypt the particular algorithms within a file in your application's bundle, and require the user of this application to decrypt this file into memory with the correct (difficult) password. That way, even if the "bad guys" were to gain access to the application, they wouldn't have everything they need to access these algorithms and would have to brute-force the password on the encrypted portion. This could be done on a standard, non-jailbroken device.

The U.S. Army is rolling out iPods in the field, with custom applications on them, so I'm sure that you're not the first person facing this challenge. If this work is being funded through a Department of Defense SBIR grant (or similar), you may even be able to contact your contracting officer and see if they can put you in touch with people at the appropriate agency who may be able to help you out with this (or even determine if it an issue to begin with).

Answer 8

I would use the built in encryption to store the data, with a key the user has to enter to decrypt it. Without the key it doesn't matter if the data blob is recovered from the device.