Re: NSA Spy Machine and DES

It is entirely possible that the Cray SIMD machine will use
Xilinxs. The folks at the Supercomputing Research Center
in Bowie are also building machines with these Xilinxs.
They're known under the name "Splash" and they've built
at least two generations. One of the architects told me
that the machine was only good for "deeply pipelined"
processes. There is one preprint, for instance, that describes
how to do text searching with the machine. (Surprise.)
Much of this should be public because the folks from the SRC
often go to conferences and present information. Two names
on the Splash project that I can think of are Buell and Arnold.
If anyone can dig up papers on this topic, I would be intrested
to read them.

That being said, I still don't really see the advantages of Xilinx.
But this really could be because I've never programmed the machines
nor have I used them for anything. It just seems unlikely to 
me that DES can be done that much faster. 

But like I said, what do I know? I would be intrigued if someone
could run a back of the envelope calculation on building a machine
with Xilinx. How many processes can you do with it? How many testing
circuits can you fit on a chip? How fast will these circuits go? 
What is the big win from pipelining the process? Sure you can 
build a sixteen stage pipeline, but will you need to put copies
of the SBOXes at each stage? How much space will this take? How
deep will the gates be? What is the gate delay at each stage? 
What will be resultant speed? 

The fact is that for all of DES's bitwise 6-to-4 sboxes and other weird
stuff, it isn't that hard to implement in a RISC processor that has
XOR, AND, shifts and fast table lookup. 

Any answers out there?

-Peter

On Aug 19,  1:12pm, Peter Wayner wrote:
> But like I said, what do I know? I would be intrigued if someone
> could run a back of the envelope calculation on building a machine
> with Xilinx. How many processes can you do with it? How many testing
> circuits can you fit on a chip? How fast will these circuits go?
> What is the big win from pipelining the process? Sure you can
> build a sixteen stage pipeline, but will you need to put copies
> of the SBOXes at each stage? How much space will this take? How
> deep will the gates be? What is the gate delay at each stage?
> What will be resultant speed?

You seem to be assuming here that DES cracking is all this machine will
do, which is something I really doubt.  As Phil Zimmerman pointed out some
time ago, there are lots of other interesting applications which SIGINT
operations perform.  Signals analysis is one he mentioned, and I'd also add
the computationally expensive tactical and traffic analysis operations
(ie. scanning masses of data items searching for significant correlations).
Examples of this might be noticing an increase in the use of enciphered
military comms from one country's border, and thus deducing (without
necessarily breaking the cipher) that a military buildup is occuring
along this border.  Sure, this sounds easy, but if your surveillance network
intercepts a hundred thousand transmissions worldwide per day, correllating the
lot for this sort of information is not a simple task.  Amusingly, such
mass analysis is now filtering down to the commercial level, and the term
which is used is "data mining".

You might also like to consider the automated analysis, sorting and indexing
of the terrabytes of textual information which the NSA would intercept every
day.  There is no way they could ever employ enough people to read it all, so
it is almost certain that automated sieves are being used for this application.

In summary: the NSA does more than breaking codes, and their computers are
not only used to run through lists of keys for DES encoded intercepts.

							Ian.