114

If you, as a nation, have the capability to decode communications, then why give that up? This is a fallacious assumption, and probably the source of your confusion. Destroying the bombes did not amount to the British "giving up" their code breaking capabilities, as the bombes were essentially mechanical ASICs, designed specifically to break the encryption ...


72

Short Answer Allied superiority in cryptography versus both the Germans and the Japanese can be broadly attributed to (1) better/greater coordination among personnel, awareness of vulnerabilities, and allocation of resources for breaking enemy codes and, (2) the fact that Axis codes were (mostly, though not always) more easy to break than Allied ones. ...


71

During that period, both Churchill and Roosevelt were old men more used to hand written letters than "high technology" teletype writers. Teletype writers are NOISY! Using teletype writers can be a slow process & thus make a l-o-n-g conversation. Telephones, despite sophisticated encryption technology, are immediate and more intimate. In ...


47

To answer why they denied its existence, because the value of British code breaking relied on keeping their ability to break codes secret. (Sorry this is without sources, I'm on a phone on a train.) Part of the wild success of British code breaking during the war was due to the Germans never realizing their communications were compromised. The Germans ...


28

Most people who worked on Enigma code-breaking didn't know the real name of the system, or the scale of the effort being made. That contributed to the secret of the breaking of Enigma being kept until the 1970s. So "appearing less threatening" is a non-issue. The few nations who know, already know, and have better cryptography. Nobody else knows. The ...


19

The Enigma machines and the breaking of the Enigma code were not the main determinants of the outcome of World War II, but did contribute to the outcome. There were only a few types of Enigma machines, so they had to be capable of using different encryption keys. If machines used the same encryption key for message after message, the encryption would be ...


19

The boarding party led by David Balme approaches U-110. Source: World War II Today With regards to keeping the capture of the Enigma and codebooks from U-110 a secret (i.e. keeping the German POWs from revealing this to anyone), the German POWs did not know the U-110 was successfully boarded: A number of schemes had been devised to capture these [...


18

If you, as a nation, have the capability to decode communications, then why give that up? This is independent of whether or not the Enigma machines were destroyed -- that ability should, if nothing else, discourage others from even trying, or at least give a head start in case someone did try to use encrypted communications. The knowledge that your ...


17

To understand why the Ultra secret had to be kept secret, one has to look at the encryption technology that was in use during the post war period, and in many cases is still in use today. Although we may consider the German Enigma machines just technology from the second world war, most people never imagined that that technology continued to be in use for ...


14

For a print work I recommend Francis L. Loewenheim, Harold D. Langley, & Manfred Jonas, Editors; Roosevelt and Churchill: Their Secret Wartime Correspondence, Dutton, 1975. Contains some 600 or so of the more than 1700 cable messages which passed between Roosevelt and Churchill from shortly after the start of the war in 1939 until April 1945. Or if you ...


12

Firstly, there is nothing 'foolish' about it. Military planning is about contingencies. The Japanese listening stations had received a report, they forwarded that report using a code they believed to be secure, and the planners modified their plans for the attack on Midway to deal with the contingency that it may have been true. The Japanese believed ...


11

I think it's safe to conclude that no fighter plane radios were encrypted, due to requiring extremely bulky equipment at the time. Communication between enemy fighters was theoretically possible, since all you need to do is tune in to the enemy's frequency, but most planes could only use a very limited set of preset frequencies. Of course this does mean ...


9

The most obvious single battle that was influenced by ENIGMA may, ironically, be the (early stages of the) Battle of the Bulge. Hitler's paranoia had finally advanced to such state in 1944 that he was convinced the Allies were eavesdropping on his intelligence; so he insisted that all plans drawn up for that attack NOT use the cracked cypher. It is likely ...


8

According to "Marching Orders", Enigma had a decisive impact on the (Second) Battle of El Alamein. Montgomery's first attacks were thrown back with heavy loss. Under different circumstances, he (or another commander) might have broken off the attack (as General US Grant did at Cold Harbor, in the Civil War). But Enigma alerted Montgomery to the fact that ...


8

Soviet Union in that time? As a quick aside, we would know that the Soviet Union did not use any forms of encryption at this time as the Soviet Union did not exist yet. The ratification of the USSR occurred in December 1922 (a year after the conclusion of the war at the Treaty of Riga in '21). Bolshevik or Soviet Russia would be the appropriate party to the ...


8

"Allies" capturing Engima machines (what you really mean was British navy, who then in Hollywood were magically transformed into US navy) was really of no importance. What was important was capturing code books. The wiring of the Enigma machine was known since the 1930s, when Polish mathematicians managed to reconstruct it from very limited information. ...


8

Submarines weren't the only source of Enigma machines. The Poles had already worked on the code and the machine before WW2 began. Marian Rejewski cracked (a large part of) the code. The Poles gave the stuff they had to the Allies before the fall of Poland. In fact, the British didn't crack the Enigma code. The Poles did that. The British raided the German ...


7

As per a few comments here: They weren't all destroyed. Reading a few books on the times there's strong hints that at least some capability was retained - both Bombes and more advanced equipment. The Brits captured many Enigma machines and also the more advanced Lorenz (if memory serves) which they could also break. Both were either used by/sold to allies ...


7

Encryption can very well be done on quite small portable devices, also during WWII. The famous German Enigma machine was about as large as a type-writer, and that was one of the most advanced and complex encryption of the time. Smaller machines with simpler encryption also existed. However, encrypted communications required a separate radio person who does ...


7

The information on this subject is scarce. We positively know that Tsarist army during WWI had all the sorts of contemporary cryptography, but the Red Army got only a small part of it. First special cryptographic service in Soviet Union (or Soviet Russia back then) was created only on 5th May, 1921. And it definitely took a few years for the new service to ...


6

Yes. (Note: I started writing a broad answer of various methods to make strong encryption ineffective, rather than banning it outright, and their consequences... but it quickly got off topic. Then I realized that Tor talk basically covers the whole topic and has plenty of examples of encryption bans. Watch the Tor talk at the end.) There are few examples ...


6

Yes, they do allow multiple keys. Typically they had a new key every day. See this Wikipedia article: Though Enigma had some cryptographic weaknesses, in practice it was German procedural flaws, operator mistakes, laziness, failure to systematically introduce changes in encipherment procedures, and Allied capture of key tables and hardware that, during ...


5

I'm not sure if this is what you are looking for, but the A-3 Scrambler system was developed in 1939 by Bell Labs. It allowed supposedly secure communications between Roosevelt and Churchill as the Second World War broke out. In reality the scrambler was very insecure and rather easily broken by the Germans. So between 1942-3 Bell Labs developed as a ...


4

The very breaking of Enigma - by Turing et al using Bombe and also by pinching of the German Naval codebooks - gave the British a blind spot that did nearly cost them the war. That blind spot was that German Naval Intelligence had broken the British Merchant Marine codes in 1938-9 and was reading transmissions using that code into 1944. The British never ...


3

The destruction of the Colossus code breaking computers was a more significant thing, I gather the reasoning was the if the machines were retained other powers would pursue such technology. Britain had their own cipher machine typeX, there was some fear that if the cipher breaking machines became general knowledge then other powers would develop it and be ...


3

Japanese didn't realize their code was partially broken, and their beliefs were less important First thing you need to understand is that Japanese naval code JN-25 was already partially compromised before the events with fake water supply problem. In fact, Americans already knew there soon would've been operation at objective "AF". Rochefort suspected it ...


2

I know a case quite a time back. During the Sino-Japanese War, an acquaintance of my family let a mechanical encryption device for the Chinese telegraph code of his design be patented. The telegraph code was in 4 decimals for each (of the more frequently used) Chinese glyphs. The device had 4 discs (out of a set of different discs, selected according to a ...


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