Undeciphered Enigma message

[Man]

As is well known, one of the main vulnerabilities of the Enigma encryption machine was that it never encoded the letters of the original message into the same letters of the ciphertext. It was this weakness that became the key to cracking the algorithm and reconstructing the ingenious mechanism.

Despite this, one undeciphered message still remains. It is dated May 1, 1945 (pictured).

Ciphertext:

JCRSAJTGSJEYEXYKKZZSHVUOCTRFRCRPFVYPLKPPLGRHVVBBTBBRSXSWXGGTYTVKQNGSCHVGF

Message serial number: P1030680 (U534).

"Enigma"​

The photographs below show two versions of the Enigma, an earlier one on the left and a more advanced one on the right with expansion boards under the keyboard that added layers of complexity.

The machine worked simply: ciphers (settings) were changed by rotors on the top left. Three rotors in 26 positions and an additional panel with ten pairs of letters gave almost 159 quintillion combinations of settings.

The message was then encrypted automatically: the operator pressed the original message key on the typewriter - and the ciphertext letter appeared at the top. This is how the message given at the beginning of the article was encrypted.

The first Enigma was made in 1923 (Model A). The cipher machine itself was invented by German engineer Arthur Scherbius shortly after the First World War. He patented the mechanism and began selling the product on the commercial market. The first major buyer was the International Postal Union, with branches all over the world. Soon the military became interested in the new product.

The first model for the army was made in 1925 and was called Funkschlüssel C. The last one was released in February 1942.

The four-rotor Enigma M4 model, released on order of the Navy on February 1, 1942.

Various versions of the Enigma were used by the armies of various countries, including Switzerland and the USSR.

"Enigma" in the Soviet army, source

Sherbius himself died in 1929 as a result of an accident with a carriage.

Cryptanalysis​

On a tour of Bletchley Park they tell a story about how the radio operators once intercepted a coded message that didn't contain the letters Z, and since that was statistically unlikely, they assumed that the message consisted entirely of such letters. And so it turned out. It was a friendly coded message from a bored German operator to his friend, consisting only of the letters Z. Then the code was cracked, and then the design of the rotors of the device .

In fact, the cryptanalysis of Enigma was a complex task, in which English mathematicians led by Alan Turing also helped. But it was the Polish cryptographers who took the lead. They were the first to think of involving mathematicians in deciphering back in the mid-1930s, when linguists were doing it in Great Britain.

The Poles built the first electromechanical machines ( cryptological bombs ) that simulated the operation of Enigma, going through all possible settings in search of the current rotor combination.

All of the Poles' developments were given to Alan Turing's group, who brought them to their logical conclusion. It turned out that the German ciphers changed once a day:

And the digital codes for the ciphers were related to the first three symbols of the message:

It was assumed that the first three letters were indicated randomly in each message, but the operators often forgot to change them so often.

This is how, after several years of intellectual work by a joint team of cryptographers and mathematicians from Poland and Great Britain (with the help of French agents who obtained the design drawings), the German encryption machine was restored, which played a very important role in the victory of the Allies in World War II. According to some estimates , the work of mathematicians and cryptographers shortened the duration of the war by about two years, saved countless lives and really changed the course of history.

P.S. The decryption of the last message of "Enigma" is being carried out within the framework of the distributed project Enigma@Home. You can join it by allocating a little power of idle CPUs.

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