Hi everyone, I found the great question on booting encrypted drives, and since I’m somewhat paranoid I’d like to ask a follow-up:

When the key to decrypt the drive is input into the system, I’m assuming it stays in the RAM till the time the computer shuts downs. We know that one could, in theory, get a dump of the contents of the RAM in such a state, if done correctly. How would you deal with this problem? Is there some way to insert the USB, decrypt the drive, and then remove the USB and all traces of the key from the system?

Thanks!

Edit: link to the question I referenced: https://feddit.de/post/6735667

  • mumblerfish@lemmy.worldEnglish
    6·
    10 months ago

    The key needs to be available to continue to be able to decrypt the data on the device. All encrypted data is not decrypted as you mount or unlock your encrypted device, that is done one the fly as you use it.

    The attack you are thinking of should also not be relevant. What you worry about appears to imply that you are more concerned about the key being protected, rather than the data the key protects. You seem to wish to have your decrypted data available, but not the key.

    • MigratingtoLemmy@lemmy.worldOPEnglish
      2·
      10 months ago

      Thank you, I realise that what I’m asking for might not be physically possible. I’m certain that RAM loses all of its contents after a loss of power, but would it be possible to pad the RAM before/during the shutdown process to make sure that nobody gets to the key?

      • aard@kyu.deEnglish
        9·
        10 months ago

        Yes, but: somebody trying to attack your machine that way would cut the power and try to freeze your memory modules. So that mitigation wouldn’t trigger.

        If you think you really need to guard against that attack you’d have to look into physical security: At room temperature there’s a pretty short window available for saving the contents. So if you manage to remove access of possibly used cooling agents to the memory modules you already made things quite tricky.

        Now if you can make removing the memory modules hard as well, and prevent booting anything but what you want to be booted there’s a decent chance it’ll be impossible to recover memory contents.

        If that still isn’t good enough you’d have to look into providing a means of physical destruction of the memory modules triggered by a backup power source inside the case on unexpected power loss.

        • MigratingtoLemmy@lemmy.worldOPEnglish
          2·
          10 months ago

          Thank you for the comprehensive answer. I will go through it again and attempt to implement some of these mitigations.

          Thanks again, I saved your comment

          • aard@kyu.deEnglish
            8·
            10 months ago

            Take into account that your average police raid will not attempt that - they just don’t have the means for that.

            If you have managed to become an important enough target that either specialists get called in, or you’ve managed to become target of three letter agencies or the equivalent in your country you will have been targeted by other attacks to gain access to your data, both software and hardware - and if you have to ask that kind of question here you’re very unlikely to successfully defend against them.

            • MigratingtoLemmy@lemmy.worldOPEnglish
              1·
              10 months ago

              Thanks for your reply. Fortunately, I am not a person under such scrutiny, and the only reason I ask this is because I’m paranoid.

              • aard@kyu.deEnglish
                4·
                10 months ago

                This level of paranoia isn’t really compatible with modern hardware, and requires a lot of effort.

                You’re pretty much limited to stuff that has open firmware available, and even then you have to hope there are no bugs or backdoors in the hardware.

                For the intel world almost everything with open firmware is pretty old - some nowadays unsupported, which means no longer microcode updates. And those microcode updates also are a problem - you can’t mitigate everything in kernel space, so usually you’d want them, but they’d also be an attack vector against you.

                And even if you manage to trust the computer itself there are a lot of attack vectors surrounding it. Do you have anything capable of recording audio in the same room as your computer? If yes, not a good idea - it has been proven possible to extract passwords from audio recordings of a keyboard. Does the room have windows? That counts as an audio recording device.

                If you got rid of that, do you have some other hardware with sensors? There’s a high chance that a device placed on your desk containing an accelerometer would also be capable of extracting your password.