Suppose the manufacturer exerted no control over the device. No code signing, no sandboxing, no security hardware, etc. Then <i>anyone</i>, not just the manufacturer, would be able to replace the PIN verification routine.<p>If the manufacturer&#x27;s ability to sign code is a backdoor, then <i>so is absence of code signing</i>.<p>You&#x27;re assigning them the moral failure to perfectly secure the iPhone only because they have tried to secure it at all. It&#x27;s subject to strictly fewer attackers; in my book, that&#x27;s a good thing.