PGP source code
Tom Thomson
tthomson at linkguard.com
Tue, 4 Sep 2001 19:30:47 +0100
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> > Although BYTE talks about "checksums", the microcode is signed (I am
> > told on excellent authority [though admittedly, my memory
> may not be as
> > good as the authority!]) by a 2048 bit RSA key...
> >
> > There is indeed, as BYTE says, very little documented about this on
> > Intel's site (and certainly no mention of RSA or of the way that the
> > chip checks the signature), though there is occasional mention of
> > microcode upgrades for chips such as the Xeon.
>
> <http://developer.intel.com/design/pentium4/manuals/24547204.pdf>
> Section 8.11.3 (pg 309)
>
> Based on my reading of the details given, it is not talking
> about a RSA
> style of signature. I might be wrong though, it is lower
> level then I am
> use to dealing with.
>
You are right, the checksum is clearly defined in table 8-7 on page 305.
It's a simple checksum, not a signature.
Tom Thomson
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<P><FONT SIZE=3D2>> > Although BYTE talks about =
"checksums", the microcode is signed (I am</FONT>
<BR><FONT SIZE=3D2>> > told on excellent authority [though =
admittedly, my memory </FONT>
<BR><FONT SIZE=3D2>> may not be as</FONT>
<BR><FONT SIZE=3D2>> > good as the authority!]) by a 2048 bit RSA =
key...</FONT>
<BR><FONT SIZE=3D2>> ></FONT>
<BR><FONT SIZE=3D2>> > There is indeed, as BYTE says, very little =
documented about this on</FONT>
<BR><FONT SIZE=3D2>> > Intel's site (and certainly no mention of =
RSA or of the way that the</FONT>
<BR><FONT SIZE=3D2>> > chip checks the signature), though there is =
occasional mention of</FONT>
<BR><FONT SIZE=3D2>> > microcode upgrades for chips such as the =
Xeon.</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> <<A =
HREF=3D"http://developer.intel.com/design/pentium4/manuals/24547204.pdf">=
http://developer.intel.com/design/pentium4/manuals/24547204.pdf</A>></=
FONT>
<BR><FONT SIZE=3D2>> Section 8.11.3 (pg 309)</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> Based on my reading of the details given, it is =
not talking </FONT>
<BR><FONT SIZE=3D2>> about a RSA</FONT>
<BR><FONT SIZE=3D2>> style of signature. I might be wrong though, it =
is lower </FONT>
<BR><FONT SIZE=3D2>> level then I am</FONT>
<BR><FONT SIZE=3D2>> use to dealing with.</FONT>
<BR><FONT SIZE=3D2>> </FONT>
</P>
<P><FONT SIZE=3D2>You are right, the checksum is clearly defined in =
table 8-7 on page 305. </FONT>
<BR><FONT SIZE=3D2>It's a simple checksum, not a signature.</FONT>
</P>
<P><FONT SIZE=3D2>Tom Thomson</FONT>
</P>
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