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Joined 3 years ago
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Cake day: June 16th, 2023

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  • Are you sure that you cannot tamper with anything with a password in the UEFI bios?

    Without a password, anyone with physical access to the computer could enter the UEFI menu and disable Secure Boot, allowing them to load an unsigned or malicious operating system.

    Does the UEFI encrypt and sign everything correctly or could you just exchange/ probe a flash chip on the mainboard and still get access?

    Many modern CPUs (like those using Intel Boot Guard or AMD Hardware Validated Boot) have a public key burned into the processor’s fuses. The CPU verifies the UEFI firmware’s signature before it even begins to execute. If the flash chip is swapped or modified, the CPU will detect the signature mismatch and refuse to power on the system.

    Or - in case of boot priority: How does your UEFI react if I disconnect all internal drives and only plug a bootable USB drive in? will it happily boot from the only possible (and new) option? Might it save that option for the next time?

    If you are using custom Secure Boot keys, then the boot device MUST use those keys. If you plug in a bootable USB drive that doesn’t have a properly set up bootloader with the correct keys, you will see an error message.

    How does your password work, when I reset the UEFI with the little jumper/button? Etc.

    Secure Boot uses a hierarchy of keys stored in the NVRAM. If you replaced the factory default keys (the Platform Key and Key Exchange Keys) with your own custom keys to sign your own bootloader or kernel, those custom keys are stored in the same volatile area that is wiped during a CMOS reset. When the reset occurs, the system deletes your custom keys and reinstalls the manufacturer’s default keys.

    Because your OS bootloader was signed with your custom keys and not the factory defaults, the UEFI will now see the bootloader as “untrusted” or “unsigned.” This results in a Secure Boot violation error, and the system will refuse to hand over control to the OS.


  • Im sure it allows that, but if your disk isnt encrypted, any files you have can easily be tampered with just by running a live boot environment from a cd/usb, or by transferring the disks to another machine.

    Secure Boot verifies the kernel/system has not been tampered since the last system update occurred. During that process, the updated files are signed against your UEFI firmware. If an evil maid has access to your files, they can replace the kernel/system files with malicious versions, then re-sign against your firmware, and you would never know the difference.

    Thats why it’s important to encrypt the data stored on disk and have your UEFI BIOS secured with a password. Makes it so evil maids cant easily create/delete boot keys and tamper with your Secure Boot, or change the boot priority to a live cd/usb.







  • Its not perfect by any means, but its getting better exponentially. Im hearing from people who have been in software development and cyber security for decades saying that at this rate, we might eventually hit bug-free code. Im optimistic of the technology, but I also subscribe to the idea that its going to peak at some point and thatll be its limit. Its also not sentient, and I’m fairly certain it’ll never be, as much as the sci-fi folks are suggesting it could be.

    I also understand the environmental impact this is taking on this planet, and I wholeheartedly believe that anyone who is using this tech absolutely must power it with renewable energy that has low to zero emissions. We needed legislation yesterday, but today would also be a good day to pass laws with strict requirements.