For Enigma fans

[David Hansen]

On 29 Mar 2009 at 13:52, Dave Howe wrote:

> I was under the impression that the bombe was not "based on" the bomba,
> but was an near-exact duplicate.

It was very much simpler and relied far more than the bombe on reducing 
the problem to manageable levels by "hand", before putting the problem 
to the machine. Imagine something the size of an ice cream box mounted 
on a tricycle or hand cart. ISTR bomba was a brand of ice cream. Some 
of those involved wrote a book on the subject, which I cannot find at 
the moment, which had drawings and the method of operation.

The bombe didn't spit out German but came up with possible settings to 
try by "hand". Once the correct settings had been worked out the bombes 
were used for the next job while the German was produced on British 
TypeX cipher machines modified to emulate an Enigma.

The bomba could test even fewer combinations and so was used with far 
more extensive "hand" work before and after using the machine. 
Presumably when the settings had been worked out German was produced on 
the copy Enigma machines the Poles had produced from their examination 
of the real thing.

IIRC changes introduced by the Germans in the late 1930s made the bomba 
fairly useless, unless very lucky. The Poles needed to produce a far 
more powerful machine to continue reading the messages but had neither 
the time nor the money to do so. As I understand it this was the main 
reason for the Poles calling in the French and British to tell them 
everything the Poles knew and give them drawings and a copy Enigma 
each. We owe a great deal to the generosity of the Poles, who we then 
abandoned to Stalin. 

> In addition, I thought they were not destroyed after the war, but saw
> service decrypting diplomatic mail (as several embassies still believed
> the enigma to be secure and used it for their diplomatic traffic)

Some were reputed to have been moved to Cheltenham and lasted until the 
1960s or early 70s, by which time Enigma machines and the like were 
wearing out, but most appear to have been broken up.

Enigmas were given to Commonwealth countries, I had a friend who used 
to operate them for the navy of one of these countries. They were 
clever enough to work out that something given to them by the British 
might well be breakable by the British but given that their great enemy 
tended to be another Commonwealth country that didn't matter as much as 
stopping the great enemy from reading communications. India and 
Pakistan are the best example.

-- 
  David Hansen, Edinburgh 
 I will *always* explain revoked encryption keys, unless RIP prevents 
me   
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54