PGP source code

[Richard Clayton]

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In article <005601c1352a$1ad80db0$1e01320a@drizzt>, Nexus
<nexus@patrol.i-way.co.uk> writes

>Add to that the number of complete loonies that devote large amounts of
>their time to actually looking for undocumented features...
>http://www.x86.org/secrets/intelsecrets.htm
>
>Kinda shames my finding the undocumented Z80 opcodes by hand ;-)

In 1997 there was a great deal of interest in an announcement by Intel
of "programmable microcode" such that 2K chunks of microcode could be
replaced at POST time (when you first switch the machine on) so as to
correct bugs (such as the "floating point problem" that caused them so
much PR trouble).

There's a little more in this October 2000 BYTE article:

        http://www.byte.com/documents/s=479/BYT20001016S0006/

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.

I have also been given to understand that there are very significant
difficulties in getting the microcode to do what it is supposed to do...

... so having it do further undocumented things as well - such as
producing security problems on end-user systems - is currently seen to
be well beyond the State of the Art.

- -- 
richard @ highwayman . com                       "Nothing seems the same
                          Still you never see the change from day to day
                                And no-one notices the customs slip away"

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