From: jac54@cas.org ()
Subject: Re: Ultrasecret (Enigma)
Organization: Chemical Abstracts Service, Columbus, Ohio
Date: Tue, 5 Jan 1993 11:57:01 GMT

In article <93004.212754VPN1@psuvm.psu.edu> <VPN1@psuvm.psu.edu> writes:
>Jim Feeney asked about radar vs.  code-breaking in the Battle of Britain.
>
>According to _The Ultrasecret_, by Winterbotham (an RAF Wing Commander or
>Group Captain personally involve):
>
>Some poles working in Germany deduced their factory was making code
>(actually, cipher) machines, called "Enigma." They smuggled out all the
>parts, which were sent to Britain.  At a country house called Bletchley, a
>group went to work to exploit this incredible intelligence coup.

	The Poles did a lot more than this.  They actually developped
	the mathematical basis for breaking Enigma.  They passed this
	on to the French, who passed it on to the British (discreetly, in
	the middle of Victoria Station to the head of MI6 who was wearing
	white tie and tails. [Seriously])

>
>It wasn't duck soup because the "key" was changed daily, but a significant
>number of top-level German messages were deciphered.

	Depends, Naval Enigma was much more difficult to break than
	Luftwaffe E, which was broken almost daily.  A lot of intelligence
	came from radio traffic analysis (invented by Gordon Welchman,
	see his excellent book "The Hut Six Story").  This indicated
	who was going to be busy next day.  Reading Enigma took longer
	and it was useful for long range planning but not for immediate
	tactical info.
>
>It was in fact the "ultra" secret, and extreme measures were taken to keep
>the Germans from finding out.  Winterbotham says the Brits read the message
>that Coventry was to be flattened in retaliation.  Churchill decided to do
>nothing, but to let Coventry be bombed and many people killed, because to
>take any unusual action would tip off the Germans, and render the "ultra
>secret" useless for the remainder of the war.

	A controversial topic.  It seems that the information that
	Coventry was the target came too late to do too much about
	defending it, what was done was too little, too late.  Churchill
	was however, prepared to make such a sacrifice.

>I'm uncertain about this, but I think it may have been an Enigma machine
>that the Brits gave us (the Germans having supplied the Japanese) that
>enable us to read the message that enabled the fleet to ambush the Japanese
>at Midway.  Perhaps someone else can clarify this.

	The Japanese PURPLE machine was broken by a U.S. group led
	by William Friedmann and Lambros Callimahos.  This was a
	stupendous purely cryptographic achievement and carried out
	independently of the European attack on Enigma.  The U.S.
	was not let in on Enigma until well into WWII (but I think
	before Dec 1941).  Breaking Purple was the greater cryptographic
	achievement, breaking Enigma was the better espionage operation.

>There is a huge literature on the subject of ciphers and codes, and the
>people who invented them and broke them; and it is fascinating.

	I recommend keeping an eye out for the "temporary, independent
	FAQ" on sci.crypt.  It contains a good bibliography.

	Alec Chambers
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