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On the most recent iPhone, data isn't encrypted based on a 4 digit PIN. It uses a tremendously long piece of data as the encryption key, but the encryption key
by beeboop 11y ago
On the most recent iPhone, data isn't encrypted based on a 4 digit PIN. It uses a tremendously long piece of data as the encryption key, but the encryption key is only accessible through some special hardware they have (which is essentially tamper proof and brute-force proof) with the 4 digit PIN. But as you said, since they can remotely update the software for this special piece of hardware, it is still susceptible to being compromised.
A lot of the conversation happening in regards to this FBI case is only due to it being an older iPhone that doesn't have this special hardware. Which is why people are confused with the FBI chose this case as their poster child when it would have made a lot more sense with the most recent iPhone.
- hartator 11y agoWhat's the "tremendously long piece of data as the encryption key"? Are you refering to the 6 digit code?
- russgray 11y agoNo, they're referring to the 256-bit AES keys in the CPU and Secure Enclave, which are entangled with the user PIN to derive the crypto key.
- bogomipz 11y agoWould you explain how 256-bit AES keys CPU and Secure Enclave and user PIN all work together to provide encryption on the iPhone? Is this documented anywhere? Is this same method employed across different generations of iPhones? Thanks
- russgray 11y agoApple's description is here https://www.apple.com/business/docs/iOS_Security_Guide.pdf https://www.apple.com/business/docs/iOS_Security_Guide.pdf, and you can find varying quality of discussion in the media by searching for Secure Enclave. Basically, the Secure Enclave contains a 256-bit AES key physically fused into the silicon during the chip fabrication process. Apple don't know this key, and neither do the manufacturers. It's different on every iPhone. The key cannot be read by any software, or the OS, or even firmware. All that can be seen is the result of using it in a crypto operation. The key used for actual encryption on iOS is derived by taking an intermediate key derived from the PIN, and then entangling it with the Secure Enclave key (and, I believe, the CPU's key, which is also unique and fused into the hardware, but not quite so secretive). This effectively ties the crypto process to the phone - if you take a data dump of storage and try to brute force it on some more powerful kit, cracking the PIN isn't enough. You'll also have to crack both the AES keys. This isn't universal across all iPhones - I think the 5S onwards have it.
- bogomipz 11y agoAwesome. Thank you! I'm guessing Android doesn't have anything like this being that there's no single chip SoC design across Android phones.