On Sun, Jun 17, 2012 at 4:30 PM, Florian Philipp <li...@binarywings.net> wrote: > Am 17.06.2012 20:56, schrieb Sascha Cunz: >> I was under the impression that it should at least help in that scenario. >> OTOH, if it takes a compromised system or physical access to the machine in >> order to manipulate the boot sequence, then I no longer understand what the >> boot sequence in such a system must be protected against (Assuming that the >> primary reason for boot sequence manipulation is to later on compromise the >> system). >> > > Well, it does help, especially when you also prevent changing UEFI > settings with a password. However, there are so many variables and > possibilities when talking about attacks on physically accessible > systems, that you're usually screwed anyway.
I'd view secure boot as complementary to TPM. TPM keeps somebody with physical access from being able to access important information on your computer, since that data would be encrypted and the keys would not be surrendered by the TPM module without a proper chain of trust. TPM is potentially more secure, although it has a fatal flaw in that if the OS is compromised then the keys can be obtained (since the OS needs the keys to access the disk) and a trojan can be installed on the bootloader. That trojan is difficult to remove or even detect even if you update your virus scanners/etc. Secure boot keeps trojans out of the early boot chain, making them easier to clean up once your system is further updated. Secure boot is also somewhat easier to implement, and a bit more recoverable if things go wrong. If you're using TPM and trusted grub and all that, then if you mess up your trusted boot chain then you may never get back the contents of your drive, unless you kept a copy of various keys elsewhere. Rich
