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  • Thanks Rod. "You're operating under the misapprehension that PKs are tied to ESPs". Microsoft states "Access to a partition is controlled by the system firmware before the system boots the operating system". How can the firmware limit access to a partition for a Boot Option if not by a particular Platform Key? I understand signing, but how about if PK1, PK2, etc are used as a principal in a simple ACL (I'm trying to figure out how the authz subsystem works here).
    – jww
    Commented Dec 15, 2013 at 18:41
  • 4
    Regarding the quote that "access to a partition is controlled by the system firmware," you're over-interpreting. That doesn't refer to cryptographic controls, but to the fact that the EFI provides drivers to give EFI programs access to partitions. Microsoft does say that it supports just one ESP. For instance, here: "Q: Can there be two ESPs on a single disk? A: Such a configuration should not be created and is not supported in Windows."
    – Rod Smith
    Commented Dec 15, 2013 at 20:16
  • 1
    @ThorstenSchöning, the page you reference does not address the number of ESPs that are permitted on a computer or hard disk, just the distinction between an ESP and non-ESP FAT partitions and how the EFI discovers and uses partitions generally. What's more, that post is somebody's interpretation of the EFI specification (as is my answer here). If you wish to challenge my claim that the EFI specification does not limit the number of ESPs, please reference the part of the EFI specification that does so. If such a limit is in the EFI specification, quoting it is an easy refutation of my claim.
    – Rod Smith
    Commented Aug 28, 2021 at 14:55
  • 1
    No, @ThorstenSchöning, the link you provided is not the EFI spec and does not explicitly say that the number of ESPs is limited. The EFI spec itself, the last time I checked, did not say anything explicit about the number of ESPs permitted on a disk or on a computer. Your claim that I need to prove this is backwards. My claim is that this information is not present in the document, which is impossible to prove except by quoting the whole document. Your claim, OTOH, that there is an explicit limit in the EFI spec is easily demonstrated, if true; just quote or reference the passage.
    – Rod Smith
    Commented Aug 30, 2021 at 14:41
  • 1
    @ThorstenSchöning, the 13.3.3 section you yourself quote is quite explicit that the EFI spec does not impose a limit on the number of ESPs on a computer. The use of the word "the" preceding "System partition" is extraordinarily weak evidence to the contrary; you have to read a lot into the use of the word "the" to draw an inference contradicting what is explicitly stated elsewhere. The explicit statement easily trumps such an inference. References to multiple "conforming FAT partitions" are irrelevant to the discussion.
    – Rod Smith
    Commented Sep 1, 2021 at 13:16