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Basically, the only good thing about the "Enigma" cipher machine was its name. Other than that, it was grossly inferior to the "Lorenz" one, apparently only used by some of the main, top-ranking persons.

If they did have a much stronger cipher machine than Enigma, why did they use the inferior Enigma for such critical and important communication? Some say that breaking the Enigma contributed heavily to Germany's defeat, so why would they risk it by not using the best machines they had?

Was it purely a matter of costs? They didn't have the time and/or money to make a ton of Lorenz ones?

The Enigma was commercially used prior to the war, making it even more bizarre that they would pick this for use in the war. It's as if somebody today would fight a war using PGP encryption -- essentially a toy created by "some person" and in wide use by normal (well, at least geeks) people today. Obviously, they would come up with some completely new encryption method and not rely on off-the-shelf products.

So why did they back then? This is something which has puzzled me for many years, ever since I learned about the existence of "Lorenz". I always used to think that the Enigma was the only and the best cipher machine they had -- probably because the winning side has bragged so much about defeating it, and the great name which suggests that it's some kind of magical "mystery box".

As far as I can tell, they never managed to break the Lorenz machine.

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    As for your analogy to PGP... good cryptography does rely solely on the key of the encryption, not on the algorithm itself being secret. That "toy" of yours -- PGP -- has been extensively analyzed; whatever "completely new encryption method" you could come up with has not (yet). One of the huge problems with Enigma was the reflector, which was thought to significantly increase the cipher strengh, when in fact it introduced what was to be the Enigma cipher's downfall -- that a character could not be encrypted to itself. Bottom line, chances are your new encryption will be less safe. – DevSolar Feb 17 at 9:37
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    The thing about Enigma was it wasn't easy to break. It took the Allies a great deal of effort to do so and doing it reliably and repeatedly involved completely new inventions (like the Bombe, effectively an automated mechanical computer). That, plus the fact that commercial Enigma hadn't been known to be cracked, meant the German judgement wasn't very wrong or foolish especially given the convenience of the portable machines. – matt_black Feb 17 at 14:01
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    "the winning side has bragged so much about defeating it" - This is hardly true. The fact that Bletchley park had read any of the encoded traffic was highly classified until the late 1970's. Winston Churchill ordered that the equipment used to perform the decryption was to be destroyed so that the secret could be kept. Many of those that worked at Bletchley and its outstations NEVER spoke about the work that was done. The secret was effectively kept for more than 30 years. – uɐɪ Feb 17 at 14:30
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    “It's as if somebody today would fight a war using PGP encryption -- essentially a toy created by "some person" and in wide use by normal (well, at least geeks) people today. Obviously, they would come up with some completely new encryption method and not rely on off-the-shelf products.” This is completely wrong. Publicly-available cryptography is better because it has been extensively tested and vetted. Cryptography you’ve developed on your own is much more likely to contain fatal flaws. – user76284 Feb 17 at 18:14
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    Obviously, they would come up with some completely new encryption method and not rely on off-the-shelf products. whoa, that is some seriously flawed understanding of crypto. rule #1 is don't write your own. rule #2 is trust ones that have been around for a long time and not cracked. PGP may or may not be in the warfighting arsenals of nations, but calling it a toy is also deeply wrong. a lot of security problems arise from bad usage/configuration rather than a flaw in the tools themselves. considering all this, how much should I trust your assertion that Lorenz was the greatest thing? – Italian Philosophers 4 Monica Feb 17 at 18:44
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The Enigma was portable. You could carry one on a small submarine, or in an armoured battalion headquarters, and they weren't a problem when an airfield had to be moved in a hurry. They didn't require mains electricity, or special communications hardware - messages were sent and received by hand using Morse code - and they were believed to be secure, provided they were used properly, and the key lists and rotors were kept out of the hands of the enemy. It was also economical to procure, and the basic technology was well-proven.

By contrast, the Lorenz did require mains electricity and special communications equipment, and was only really suited to a permanent headquarters. It was known to be more secure, but the Enigma was thought to be sufficiently secure for everything except the highest level communications, so that's what the Lorenz was used for by the German Army. It was also expensive, and complicated by the standards of the time, which made it only usable in situations like a permanent headquarters, where skilled technicians could be available.

The Lorenz was also decrypted by the Allies, from mid-1942, after considerable amounts of previous work. It is not as widely known as the Enigma decryption, because the Enigma has a cooler name, and was much more tactically important. The Lorenz gave strategic-level information, which appeals less to journalists and movie-makers.

The Siemens and Halske T52 family were another family of enciphered teleprinters, used by the Luftwaffe and Kriegsmarine. They weren't compatible with the Lorenz. The a, b and c versions were weak enough to be broken by hand, but the d and e versions were stronger than the Lorenz. The British cryptanalysts at Bletchley Park broke into these ciphers, but didn't put as much effort into them as the Lorenz. This was because the Luftwaffe often re-transmitted messages in ciphers that were already broken, or much easier to attack. Also, reading the Lorenz used by the German Army would usually tell you what the Germans intended doing.

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    Even Enigma was safe - provided you didn't know at least parts of unencrypted messages to have a guideline - as shown in the movie "Enigma". The used messages were intentionally short thus giving the decryptors an almost impossible task – eagle275 Feb 17 at 10:33
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    I have some vague memory that towards the end of the war when the Germans grew suspicious about the security of the Enigma they introduced a change which was roughly on the level of 'double the length of your pass phrase' but that was sufficient to go from easy to decipher to impossible to decipher for the allies. – quarague Feb 17 at 13:36
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    @quarague "Easy to decipher." Well, it took years of effort, including the capture of an Enigma machine by Poland, before it became easy. To me, that seems like a very substantial effort. My recollection is that they added a digit later on that made the deciphering process much more difficult. – Don Branson Feb 17 at 15:57
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    @eagle275 By 1944 they figured out "eins" ("one") appears in nearly every message and automated the process of searching. Germanic fastidiousness does not mix well with cryptography. codesandciphers.org.uk/documents/cryptdict/page34.htm – Schwern Feb 18 at 0:45
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    @DonBranson Of course it wasn't easy to decipher in the beginning. But once they had figured it out (after substancial effort) the standard Enigma become fairly straight forward to decipher. The boosted version not so much, even though the Allies knew that it was essentially the same thing but with a longer pass phrase. – quarague Feb 18 at 7:38
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I would add two more factors: cost and being invented too late.

Enigma was available commercially in 1923. The Reichsmarine (the navy of the German Republic) put it into service in 1926 and the Reichswehr in 1928 (the army of the German Republic). This meant by 1939 the German military had 10 to 15 years experience with Enigma, and German industry had experience producing it.

The Vernam cipher, upon which Lorenz is based, was invented in 1917 and some machines existed in the 1920s. But the Lorenz SZ40 didn't exist until 1940 and was not brought into operational use until 1941.

Enigma machines were relatively cheap, portable, robust, and required no external power. It's estimated 20,000 to 50,000 were produced (I don't know if this is military machines or all machines). This allowed them to be used tactically by individual ships, submarines, and division commanders. 1,100 were required for submarines alone.

Switching the German military to Lorenz for tactical communications could only happen in 1941 the earliest. It would have required producing thousands of the new, complex machines at a time when Germany was being drained of resources by garrisoning their newly conquered empire and their invasion of the Soviet Union. New protocols in using the machine securely at the tactical level (operational mistakes are what sunk Enigma and would also sink Lorenz) would have to be developed and distributed. Thousands of operators would have to be retrained on how to use the machine.

Distribution and training would have to happen from Atlantic Ocean to the depths of Russia, from the deserts of North Africa to the fjords of Norway. Unlike Enigma which was worked out in peacetime, the German military would have to learn this new device while in the middle of a high-intensity, multi-front war.

All to be cracked in about a year or two.

As far as I can tell, they never managed to break the Lorenz machine.

Tommy Flowers would be very surprised to hear that. He lead the development of machines to crack Lorenz culminating in Colossus, arguably the first programmable digital computer.

Basically, the only good thing about the "Enigma" cipher machine was its name. Other than that, it was grossly inferior to the "Lorenz" one, apparently only used by some of the main, top-ranking persons.

If anything Lorenz prove easier to crack while Enigma continued to give code breakers headaches throughout the war.

Enigma was being analyzed since the 1920s, first by the Poles, then by the British. Physical copies of the machines were available to the code breakers. The Enigma machines were continually improved with features such as the plugboard and additional rotors sending cryptographers scrambling to adapt.

In contrast Lorenz was first seen in late 1940. It was worked out without ever seeing a machine. Breaks appeared in January 1942. By mid 1942 Lorenz was being broken on a regular basis. 1943 saw machines and computers dedicated to breaking Lorenz.

Sources

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    Please change that to "I would add three more factors: cost, being invented too late, and being easier to crack". Over a third of your answer is a convincing indication of the third, and yet it doesn't get mentioned at the top with the other too. – mtraceur Feb 18 at 20:45
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    You're absolutely right. I lost focus of the original question when I got excited by the newfound knowledge that it was easier. – mtraceur Feb 18 at 21:01
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    @mtraceur An additional tidbit: British cryptographers kept their oaths of secrecy well after the war. Even in the immediate aftermath it may not have been known outside the Western intelligence agencies that either was cracked. This was to their advantage as they sold known flawed encryption devices to third parties; ones they could read. This is also why histories of the European theater written before about the 70s may not feature information about Enigma and instead repeat Allied cover stories for how they got their intelligence. This is also why Colossus is not well known. – Schwern Feb 18 at 21:04
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    "required no power." Just being a pedant, but it did, of course, require a battery, – Simon F Feb 19 at 18:00
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    @SimonF External power. I'll clarify. – Schwern Feb 19 at 18:25
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"Superior" is a subjective attribute. To use that term, you basically have to define it (faster, more reliable, etc.)

What appears to be true about the Lorenz machine is that it is more sophisticated than other machines such as Enigma. Another way of putting this is that it was more "systematic," and therefore more efficient in its workings that the Enigma machine. That's one way of defining "superiority."

That can also be a disadvantage. If a code is "too" systematic, it can be easily broken. This appeared to be the case with the Lorenz machine; British crytographers were able to reconstruct its structure before the war ended without having seen it in action, and post-war investigators found it easy to break. Enigma, by its complexity, was actually more secure (and easier to make secure).

In one method of coding messages, America used Navajo Indians (and their relatively arcane language) on both sides of the messaging system. These are human codes, but one that is non-systematic and therefore relatively unintelligible, unless you have a Navajo to decipher it for you.

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Another point: You are judging the situation from the modern perspective, in which people have learned what makes an encryption method secure and what makes one insecure. People at the time of Enigma etc were much less knowledgeable about this. For them, 'security through obscurity' was naively considered a valid way of thinking about encryption, whereas now we understand that it is really a dubious way of thinking. Actually, it was experience in breaking codes such as Enigma that helped people learn these things.

[CLARIFICATION: In the preceding paragraph, I wasn't actually claiming that -Enigma itself- used 'security through obscurity' (though the ways it was set up for use showed this feature to a limited extent); I was merely noting that -that general approach- was a common mindset (and often still is, to our detriment). I apologize for the confusion.]

Additionally, with regards specifically to Enigma: Aside from the built-in flaws of the scheme itself, breaking the code was greatly aided by some pretty bad practices in the way the Germans used the Enigma, which failed to concern them precisely because they assumed it was unbreakable. [for example, one Enigma operator chose his encoding gears by the fact that their letter identifiers matched the initials of his favorite Hollywood movie stars (or something like that); this helped the British decode his messages once they picked up on this fact]

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