A proper law

[Ian G Batten]

On Thu, 06 Mar 2003, Owen Lewis wrote:
> I agree with you. Much can be achieved both by refusing to be over-awed by a
> problem and setting aside the received wisdom as to how such a problem can
> be approached or that the problem cannot be solved.

That's clearly true.  However, the point about Enigma was that it would
fail the most basic tests for a crypto system today --- the input is
correlated with the output and is not flat random --- and it was used
incredibly badly.  And the bad use wasn't just a matter of individual
stupidity, some of it was systematic to the communications network
(stereotyped openings and closing in a system already prone to
conjectured-plaintext attacks) and even to the key setting process (the
reuse of stecker sets over time was bad, but in some senses far worse
was the policy of not repeating a the choice of wheels within a month,
which meant that by the end of the month the number of options to be
tested was significantly reduced).  

It's clearly the case that Enigma was broken by very clever people, but
we must not forget that it was used monumentally badly.  And you do have
to ask how successful Bletchley Park would have been against an enigma
which didn't have a symetrical plug board, and therefore didn't have the
non-clashing property.  If E could encode to anything including E,
rather than anything except E, whole swathes of the techniques used
would have evaporated.

To me, far more interesting are the breaks into Fish and Tunny, which on
the face of it are fairly strong systems.  My reading of the published
materials is that large amounts of what was done, and why, have not been
published, perhaps with a very good reason.

> Perhaps one example is the exciting work being done to prove that movement
> faster than the speed of light occurs. It's hard to remember now that there
> were once educated people who thought the movement faster than the speed of
> sound would be impossible.

I didn't know that that theory was advanced.  It'd be interesting to
know when: the muzzle velocity of a rifle in .303 is well over 2000fps
(speed of sound is of the order to 1000fps, depending upon altitude) and
those were available in the late 19th century.  Even .38-40 is
supersonic under certain circumstances.

Looking around at
http://www.volny.cz/buchtik/Revo/Ballistic_Info_komplet.htm, which
includes a lot of 19th century centre-fire cartridges, there are no
subsonic rifles and many of the handguns are supersonic as well.  I
accept that the ``most energetic loading'' of 9mm Parabellum today is
rather hotter than it would have been in 1914, by the way.

> Or, even earlier, that travel faster than 45 mph
> would be impossible to sustain as the change in air pressure would cause the
> suffocation of any who tried.

That's close to an urban myth.  It's alternatively said that the man who
advanced that theory was regarded as a nutcase even at the time, or that
it was never advanced in a spirit beyond that of satire.  Although
http://www.pastor2youth.com/Illustrations/P/prediction.html provides
some amusing equivalents.

ian