4 ms·

Okay, but if my password is complex enough and there is no known data inside the encrypted data then I do not see how bruteforcing would be a viable option. Ev

Okay, but if my password is complex enough and there is no known data inside the encrypted data then I do not see how bruteforcing would be a viable option. Even with a chain of trust, what is to stop someone desoldering the storage chip off my device and reading the data and bruteforcing that way? I had a long think while writing this reply about different ways of stopping the issue you described of "change[ing] the OS to simply ask for your passcode and send it back to that someone, you won't notice it", and I couldn't think of one that would be entirely secure (eg. encrypting system, extra checks for this part of the OS) so I agree there - however: - There are 100s of millions (billions?) of PCs that start and do not have a chain of trust or SecureBoot that store much more confidential information than who my mother last called. - Lots of servers that store confidential information do not have a chain of trust or SecureBoot. - SecureBoot is vulnerable. - Users who get a little popup when starting their phone would likely just ignore it. (if you disagree with this then you severely overestimate the average phone user) - The chain of trust becomes completely worthless after I decide to put a new operating system on my device. This limits my choice and freedoms as a user of a device.

georgyo 8y ago
I don't disagree with it limiting choice and freedom, but you are much more insecure. It doesn't matter how good your encryption or password is if I can change your bootloader to have a program steal that password or read the encryption key out of memory. See some of the thunderstrike attacks for examples of what a compromised bootloader can do.
wepple 8y ago
“if my password is complex enough” - fine for you, the average consumer chooses weak passwords, especially on mobile platforms. “what is to stop someone desoldering the storage chip off my device and reading the data and bruteforcing that way?” - the key will be 128-bit, not bruteforcable in the next hundred years. The TEE contains that key, and can only be unlocked by giving it your user password, online. The remainder of your arguments seem to be “well it’s not perfect, so why bother?” Servers don’t get left on the subway or stolen. Modern PCs mostly do have forms of secure boot. I can’t speak for Android ecosystem, but users won’t get a popup on iPhone, a modded firmware will just not let the phone boot.
- JoshuaAshton 8y ago
  I agree, weak passwords are a big issue. I see your point about bruteforcing that key, however I was more talking about bruteforcing the password. Servers have been stolen in the past, and I am not just talking about a big rack server here. In Android, all you tend to get is an unlock symbol on the bootloader logo, or a warning triangle.
  - wepple 8y ago
    I may be a bit confused. I apologize in advance if I misunderstood. With the desoldering the chip to read the data off, you’ll get an encrypted blob which is encrypted with a securely random 128-bit key, so it’s impossible to crack. the Key and the users password are embedded inside the TEE and cannot be read out - the TEE only provides an interface where you can supply a candidate password, and if you get it correct it’ll provide you the 128-bit key to decrypt your data. It has an internal delay and counter, and will destroy the key if you get the password wrong X number of times. So I’m not sure how you might go about being able to brute force the password, given you can only brute-force online, which is slow and will only give you a small number of attacks.
phh 8y ago
Well, I understand your opinion, though I don't agree with you. > - The chain of trust becomes completely worthless after I decide to put a new operating system on my device. This limits my choice and freedoms as a user of a device. Actually, no. If you just want to replace the operating system, you're good to go. Modern android phones display the public key of the kernel when booting a non-OEM ROM and bootloader has been re-locked. (granted, pretty much noone does that)

georgyo 8y ago

I don't disagree with it limiting choice and freedom, but you are much more insecure. It doesn't matter how good your encryption or password is if I can change your bootloader to have a program steal that password or read the encryption key out of memory. See some of the thunderstrike attacks for examples of what a compromised bootloader can do.

wepple 8y ago

“if my password is complex enough” - fine for you, the average consumer chooses weak passwords, especially on mobile platforms. “what is to stop someone desoldering the storage chip off my device and reading the data and bruteforcing that way?” - the key will be 128-bit, not bruteforcable in the next hundred years. The TEE contains that key, and can only be unlocked by giving it your user password, online. The remainder of your arguments seem to be “well it’s not perfect, so why bother?” Servers don’t get left on the subway or stolen. Modern PCs mostly do have forms of secure boot. I can’t speak for Android ecosystem, but users won’t get a popup on iPhone, a modded firmware will just not let the phone boot.

JoshuaAshton 8y ago
I agree, weak passwords are a big issue. I see your point about bruteforcing that key, however I was more talking about bruteforcing the password. Servers have been stolen in the past, and I am not just talking about a big rack server here. In Android, all you tend to get is an unlock symbol on the bootloader logo, or a warning triangle.
- wepple 8y ago
  I may be a bit confused. I apologize in advance if I misunderstood. With the desoldering the chip to read the data off, you’ll get an encrypted blob which is encrypted with a securely random 128-bit key, so it’s impossible to crack. the Key and the users password are embedded inside the TEE and cannot be read out - the TEE only provides an interface where you can supply a candidate password, and if you get it correct it’ll provide you the 128-bit key to decrypt your data. It has an internal delay and counter, and will destroy the key if you get the password wrong X number of times. So I’m not sure how you might go about being able to brute force the password, given you can only brute-force online, which is slow and will only give you a small number of attacks.

phh 8y ago

Well, I understand your opinion, though I don't agree with you. > - The chain of trust becomes completely worthless after I decide to put a new operating system on my device. This limits my choice and freedoms as a user of a device. Actually, no. If you just want to replace the operating system, you're good to go. Modern android phones display the public key of the kernel when booting a non-OEM ROM and bootloader has been re-locked. (granted, pretty much noone does that)