Newsgroups: alt.folklore.urban
Subject: Re: Crypto (was: Bugger it)
From: system@codewks.nacjack.gen.nz (Wayne McDougall)
Date: Thu, 21 Jan 93 17:05:46 NZST
Organization: The Code Works Limited, PO Box 10 155, Auckland, New Zealand

smb@research.att.com (Steven Bellovin) writes:

> In article <4dDO02yX32Oi01@JUTS.ccc.amdahl.com>, tjc50@juts.ccc.amdahl.com (T
> > In article <cN6DXB8w165w@codewks.nacjack.gen.nz>, 
> > system@codewks.nacjack.gen.nz (Wayne McDougall) writes:
> > > ObUl: IBM mainframes have undocumented machine language op-codes that are
> > > completely useless of any purpose other than for optimising cryptography.
> > 
> > Mark this one T.
> > 
> > From the IBM ESA/390 Principles of Operations:
> > 
> >       The remaining extensions of ESA/390, for which detailed 
> >       descriptions are not provided, are as follows:
> >  
> >       - The integrated cryptographic facility provides a number
> >       of instructions to protect data privacy, to support message
> >       authentication and personal identification, and to facilitate
> >       key management.  The high-performance cipher capability of 
> >       the facility is designed for financial-transaction and bulk-
> >       encryption environments, and it complies with the Data Encryption
> >       Standard (DES).
> 
> Depends on your interpretation.  I took the original message to mean that
> there were secret instructions to support cryptanalysis, and that, to my
> knowledge, is false.  In the past, there have been add-ons to aid in
> cryptanalysis, though; the best-known example is the ``Harvest'' box
> that attached to the IBM 7030 (Stretch) computer.  That one is described
> in ``Planning A Computer System'', by Werner Buchholz, Copyright 1962,
> McGraw-Hill.
> 
> So -- Wayne, before we start a rumor mill, what did you mean?

Hmmm, might get in trouble about this one.....still that's never stopped me.

My question arises as a result of a comment made by Associate Professor
Bob Doran (as he was at the time), of Auckland University, and formerly of
Amdahl Corporation. I submitted the statement here, as being a trusting sort
until I started reading this newgroup, I had always accepted it as fact.

The impression I gained was that these were indeed secret undocumented
instructions and as I recall, the comment was made that these were discovered
when someone went exhaustively through all possible opcodes to see if any did
anything useful. (eg perhaps a ROL and an ADD at the same time, thus allowing
sneaky programmers to save a cycle, as well as making their code had
to decipher, crack. I know this was done on the C64, with the 6502 which
had "unalloacted" op-codes, that would still "do things" - in a reasonable
way based on interpreting the various single bits as reasonable instructions
- some were useful, others not, others just a duplicate of existing codes,
but it tended to foil crackers, using a standard disassembler). 

So these undefined opcodes were investigated, and it was discovered that some 
opcodes did some very useful things. In particular (hazy memory) things like
a ROL as opposed to an ASL which you would normally use, unless you were
into optimising crptography.

So, I would NOT consider the examples given as proving what I thought I 
heard, but if nothiong else surfaces, I would accept that they formed the
basis of what I should have heard. Particulary as one of the correspondents was
indeed from Amdahl.

I hope your not sorry you asked me to explain what I meant?



-- 
  Wayne McDougall, BCNU

"I hate quotations." - Ralph Waldo Emerson