NSA Can Spend a Billion on a Computer

[Timothy C. May]

Whit Diffie has some more info, including a clarification, on the
differences between Hagelin and rotor machines:

Forwarded message:
To: tcmay at netcom.com (Timothy C. May)
From: whitfield.diffie at Eng.Sun.COM
Date: Tue, 12 Oct 1993 at 08h00
Subject: NSA Can Spend a Billion on a Computer

		    Minor technical point

> The Harvest machine was particularly good at brute force breaking of
> Hagelin-type rotor machines, the "DES of its day"

    Hagelin machines aren't considered rotor machines even though
their main moving elements do rotate.  Rotor machines had rotating
elements that were wired wheels implementing table look-ups, i.e.,
S-boxes.  The six wheels in a Hagelin machine merely have setable bits
around their edges.  The are in effect pieces of binary key that
rotate --- much like the C and D registers in DES.

    Feel free to redisseminate this if you like.
							Whit