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PC bootloader is totally insecure. And no, full-device encryption doesn't protect you much in my opinion. First, full-device encryption is much weaker if you c

by phh 8y ago

PC bootloader is totally insecure. And no, full-device encryption doesn't protect you much in my opinion. First, full-device encryption is much weaker if you can do offline bruteforce. With a secure boot trust of chain, it is online, and is rate-limited by the TEE (and could be made to destroy after too many tries) Even better, per Android documentation, full-device encryption key is tied to boot public key. So if someone flashes another OS, even if you enter the passphrase, noone will access your data. Also, with a PC, if someone replaces your PC, and changes the OS to simply ask for your passcode and send it back to that someone, you won't notice it. With a proper boot chain of trust (which PCs don't have, except for Librem BIOS), it is evident that the OS has been changed, so you know not to give this device your passcode. Also, boot chain of trust makes it harder to do cold-boot attacks. So globally, having a chain of trust, is much more secure for full-device encryption, because it forces online bruteforce. Considering that usually passwords used on smartphones are much more weaker (many people have 6 digits for their smartphone, vs 10 characters on their computers), the added security seem necessary to me.

snaky 8y ago
Using offline bruteforce at one hundred trillion guesses per second, https://www.grc.com/haystack.htm https://www.grc.com/haystack.htm says you would need a 15 thousand centuries to crack the password '7jk_nhAYTasd76'.
- shittyadmin 8y ago
  Yeah, if you can pick a secure password and the device is always on your person like a smartphone usually is, evil maid attacks are out as are most other blackbag techniques. The big problem is that entering a password like that is a real pain on mobile, especially on device unlock. You could potentially set a different password on boot vs on unlock - that's a tad trickier than the average user is likely to want to deal with, but entirely plausible for the paranoid power user.
  - Forbo 8y ago
    That's exactly how fingerprint locks work on the Pixel. First unlock after boot requires a password, after that fingerprint can be used. It requires password entry about once a day or so as well for additional security.
    - snaky 8y ago
      For false additional security. More than that, it makes the password effectively useless, considering how easy is to peep when user is entering it, especially when it happened at random so the probability the user happened to be at some public place at that time is high.
JoshuaAshton 8y ago
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.
userbinator 8y ago
PC bootloader is totally insecure. A good thing, IMHO. "Insecurity is freedom." "Those who give up freedom for security deserve neither."
- wepple 8y ago
  Aren’t these quotes contextual? I’m sure most people are prepared to give up the freedom of easy access to their house in order to require access with a key, as a fair trade off of security.
  - userbinator 8y ago
    If you bought a house, you own the keys. That isn't the case with these locked-down systems.
bloak 8y ago
With a PC it's easy for an attacker to modify the hardware, for example by inserting a recording device in the keyboard connector, so preventing an attacker from modifying the bootloader wouldn't add much security. Even with a typical laptop it's fairly quick and easy to replace or insert components. In general, it's funny how security bods sometimes worry about attackers modifying the hardware when the attacker could achieve the same thing more easily by completely replacing the hardware. (Is that really your phone that you just entered your passcode into, or is it an identical phone modified so as to transmit the passcode to the thief who just substituted one for the other?)

by phh 8y ago

snaky 8y ago

Using offline bruteforce at one hundred trillion guesses per second, https://www.grc.com/haystack.htm https://www.grc.com/haystack.htm says you would need a 15 thousand centuries to crack the password '7jk_nhAYTasd76'.

shittyadmin 8y ago
Yeah, if you can pick a secure password and the device is always on your person like a smartphone usually is, evil maid attacks are out as are most other blackbag techniques. The big problem is that entering a password like that is a real pain on mobile, especially on device unlock. You could potentially set a different password on boot vs on unlock - that's a tad trickier than the average user is likely to want to deal with, but entirely plausible for the paranoid power user.
- Forbo 8y ago
  That's exactly how fingerprint locks work on the Pixel. First unlock after boot requires a password, after that fingerprint can be used. It requires password entry about once a day or so as well for additional security.
  - snaky 8y ago
    For false additional security. More than that, it makes the password effectively useless, considering how easy is to peep when user is entering it, especially when it happened at random so the probability the user happened to be at some public place at that time is high.

JoshuaAshton 8y ago

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.

userbinator 8y ago

PC bootloader is totally insecure. A good thing, IMHO. "Insecurity is freedom." "Those who give up freedom for security deserve neither."

wepple 8y ago
Aren’t these quotes contextual? I’m sure most people are prepared to give up the freedom of easy access to their house in order to require access with a key, as a fair trade off of security.
- userbinator 8y ago
  If you bought a house, you own the keys. That isn't the case with these locked-down systems.

bloak 8y ago

With a PC it's easy for an attacker to modify the hardware, for example by inserting a recording device in the keyboard connector, so preventing an attacker from modifying the bootloader wouldn't add much security. Even with a typical laptop it's fairly quick and easy to replace or insert components. In general, it's funny how security bods sometimes worry about attackers modifying the hardware when the attacker could achieve the same thing more easily by completely replacing the hardware. (Is that really your phone that you just entered your passcode into, or is it an identical phone modified so as to transmit the passcode to the thief who just substituted one for the other?)