brute forcing AES256 would require computing power that, as far as we know, the NSA doesn't have. That's a very different situation than the NSA being able to

brute forcing AES256 would require computing power that, as far as we know, the NSA doesn't have. That's a very different situation than the NSA being able to force the hand of the extremely small number of US companies who are legally able to produce the baseband chipsets found in every single cell phone. All the NSA has to do is hand a single national security letter to Qualcomm and they'd be able to backdoor half of the entire market. That's just the hardware. To backdoor the software they only need to knock on the doors of two corporations.