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Date: Thu, 8 Nov 2012 11:19:28 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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Subject: Re: [RFC] Second attempt at kernel secure boot support
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> You have a fair chance of protecting via physical means (Locked rooms,
> Background checks on users etc.) of preventing a user with malicious intent
> to access the local machine.

So called "secure boot" doesn't deal with any kind of physical access,
which also means its useless if a device is lost and returned and you
don't know if it was in the hands of a third party.

> The first thing a computer does when switched on is run its first code
> instructions. Commonly referred to as the BIOS.

A good deal more complicated than that. However the signing in hardware
and early boot up on a lot of devices already goes as far as the BIOS if
the system has BIOS or EFI if it doesn't. You also have all the devices
to deal with.

> Normally digital signatures would examine the binary, ensure the signature
> matches, and then run the code contained in it.

No - it's a good deal more complicated than that too.