I don’t want anyone thinking I think Apple should set up a back door. I think it would be stupid. But I also think it’s reframing the argument away from reality. (Technically, I’m sure it would be pretty easy to generate a master decryption key pair and encrypt the device’s local key using the public part of the pair. Keeping the private part of the master pair secure is theoretically possible but entirely impractical.)

But even if Apple were to agree to add a back door, it would not help get into any currently locked iPhones. Existing iPhones have no back door installed, and would have to be unlocked to install it. If you can unlock an iPhone, you don’t need to install new software to help unlock it! Unless there’s a known vulnerability (which other parties would know about, too) it’s mathematically impossible for Apple to offer much help in unlocking an iPhone.

So there’s no argument about whether Apple should or can unlock these phones. The argument is if we want all phones unlockable by Apple or whoever else holds a copy of the key in the future (and for certain the US government would do whatever it needed to in order to get a copy).

If Apple were to be forced to install a back door, I hope it is only done to US devices. I also think that if Apple is forced to generate a back door for US phones it should look to relocate its operations and development to a safer country.