No need to be a major power.  Linux patches x86 code, as does Windows.  I ran 
across a project several years ago that modified the microcode for some i/o x86 
assembly instructions.  Here's a good link explaining it all.  

http://en.wikipedia.org/wiki/Microcode

All this hw/sw flexibility makes designing a good security system a real 
challenge.  You need a reference monitor somewhere in it that you can truly 
trust.

- Alex


> ----- Original Message -----
> From: "John Ioannidis" <[EMAIL PROTECTED]>
> To: Cryptography <cryptography@metzdowd.com>
> Subject: Just update the microcode (was: Re: defending against 
> evil in all layers of hardware and software)
> Date: Mon, 28 Apr 2008 18:16:12 -0400
> 
> 
> Intel and AMD processors can have new microcode loaded to them, and 
> this is usually done by the BIOS.  Presumably there is some 
> asymmetric crypto involved with the processor doing the signature 
> validation.
> 
> A major power that makes a good fraction of the world's laptops and 
> desktops (and hence controls the circuitry and the BIOS, even if 
> they do not control the chip manufacturing process) would be in a 
> good place to introduce problems that way, no?
> 
> /ji
> 
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