One of the greatest technical sensations of 1928 was the invention of the Berlin engineer A. Krih, heralded as a revolution in the encryption business. Indeed, the inventor proposed to replace the long and painstaking manual decryption of the text with the work of an automatic encryption machine. Krih's idea was phenomenally simple. Imagine a typewriter where the characters on the keys do not match those on the letter arms. If you tap the text of the message on such a machine, then instead of it you get a complete gibberish on paper: a chaotic set of letters, numbers and punctuation marks. But if now, on the same typewriter, tap this same gibberish, the original text of the message will automatically turn out on paper.
This simple scheme was significantly improved by Krikh. He took not a simple, but an electric typewriter in which keys and letter levers are connected by wires to a relay. By breaking the conductors and inserting an intermediate link between them - a switch, Krikh was able to mix up the wires in any order by simply rearranging the plugs on the external panel of the device. The main secret of the device was not its device, but the key - the location of the plugs, known only to the sender and the addressee.
An ordinary typist, working on Krikh's apparatus, translated the sender's text into a meaningless set of characters. With this set, which arrived by mail, telegraph or radio, the addressee performs the reverse operation and receives a decrypted message. At the same time, typists, who performed the work of experienced encryptors at high speed, might not have the slightest idea about the key, or the codes, or cryptography in general.
Crih's encryption machine was successfully tested in 1928 during the flight of one of the zeppelin across the Atlantic: radio messages from the airship were deciphered with a previously unattainable speed by the German air department and went to press. In those days, the world press advertised a typewriter weighing only 4 kg and costing only 1,500 marks. The guarantee of the secrecy of dispatches, the newspapers wrote, was complete.
Based on the commercial Krikh Enigma G machine, the military cryptographers replaced its plug switch with a more advanced and feature rich system of rotors and gears and received an improved Enigma M machine. Fleet cryptographers also made a number of improvements to this design, further increasing the reliability of encryption. In addition, the fleet, in contrast to the army and aviation, transmitted all administrative correspondence by ground communication. At the first opportunity, he laid the cable connection and used the radio only when there were no other options. But here, too, all precautions were taken.
As you know, the English fleet used only one cipher throughout the war, which was periodically amended. The Germans approached this issue much more seriously and used more than ten different ciphers. For example, the Fuhrer's surface raiders used a cipher code-named Hydra during operations in the North Seas and the Baltic, and a different cipher was used in the waters of the Mediterranean and Black Seas. The submarine fleet of Nazi Germany had their own codes. If the boat terrorized the allied communications in the Atlantic, then it was ordered to communicate with the Triton cipher, and in the event of a transition to the Mediterranean Sea, change the code to the Medusa cipher, etc. Most of the ciphers changed every month, and the small details in them changed every day. In addition, by a short signal, which was difficult for radio direction finding stations to detect, it was possible to change the code at any time. Let's say a signal composed of the Greek letters alpha-alpha prescribed the Neptune cipher, the beta-beta signal ordered the Triton cipher, etc.
The cryptographers of the fascist fleet also took care to protect their encryption system, even if the ship with the Enigma and all the instructions that came with it fell into the hands of the enemy. Instructions and ciphers were printed on paper, which had a unique property - it dissolves in water in a matter of seconds, which was supposed to guarantee their destruction in case of sinking or seizure of the ship. And if these documents nevertheless fell into the hands of the enemy, he could read the ciphers of the Germans for no more than a month, until the introduction of new code tables would throw him back to his starting position.
In short, there are seemingly good reasons to believe that the German encryption system is practically inaccessible to hacking. And if so, then the success of the Allies' struggle with submarines in the Atlantic is truly mysterious. After all, radar and radio direction finding are in themselves insufficient for effective anti-submarine warfare.
Simple calculations show that for continuous illumination of the entire surface of the North Atlantic, with the then technical capabilities, it was necessary to constantly keep 5-7 thousand bombers in the air. To ensure round-the-clock duty, this figure would have to be increased to 15-20 thousand vehicles, which was absolutely impossible. In reality, the Allies could allocate no more than 500 bombers to solve the assigned task, i.e. 30-40 times less. This presupposes some highly efficient system to narrow the search field to a level where the advantages of the radars installed on these relatively few aircraft could be manifested.
The network of radio direction-finding stations made it possible with sufficient accuracy to determine in the ocean the coordinates in which submarines, which were on the surface, exchanged radiograms among themselves or sent reports to the coastal headquarters. Moreover, there was even an opportunity to restore the routes of submarines. However, the radio direction finding data did not allow predicting the further movements of submarines, and knowing in advance where they were going to rise to the surface. Meanwhile, many commanders reported that their submarines were attacked from the air within minutes of being surfaced; it turned out that the planes of the allied aviation knew in advance the area of surfacing and were waiting for the submarine there. Moreover, the Allies suspiciously quickly detected and destroyed supply vessels, and the Allied convoys abruptly changed course and bypassed the places where the Nazi boats were waiting for them.
Some officers from Dennitz's headquarters more than once reported to their superiors that the enemy had either figured out the German naval codes, or that there was treason and espionage at the headquarters. “We checked our secrecy instructions over and over again, trying as much as possible to ensure that the enemy would not recognize our intentions,” Dennitz recalled after the war. “We were endlessly checking our ciphers to make sure they were completely impenetrable …” And each time it all boiled down to tightening secrecy measures: reducing the number of persons allowed for cipher correspondence, introducing even stricter security measures at the headquarters of the commander of the submarine forces. As for the ciphers, here the leading experts “unanimously denied the enemy's ability to read radio messages by decrypting them, and based on these intentions, the chief of naval intelligence invariably answered all doubters that the ciphers were absolutely reliable.
And yet the impossible turned out to be possible - the British split the codes of the fascist fleet. This fact was one of the most closely hidden secrets of the Second World War by the British. The first information about how this was done became known only in the mid-70s after the publication of the books of the French officer Bertrand and the British air and navy officers Wintrbotham and Beasley. But more on that in the next part….
References:
Bush H. Submarine fleet of the Third Reich. German submarines in a war that was almost won. 1939-1945
Dennitz K. Ten years and twenty days.
Ivanov S. U-boot. War under water // War at sea. No. 7.
Smirnov G. History of technology // Inventor-rationalizer. 1990. No. 3.
Blair K. Hitler's Submarine War (1939-1942). "Hunters".
Biryuk V. Secret operations of the twentieth century.
