Cipher Machines





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Hebern Machine

Hebern and his Electric Code Machine

by Ralph Simpson

The Hebern code machine, one of only 12 known to exist!
This one-rotor model is on display at the Computer History Museum, Mountain View, CA

Over 100 years ago, the Hebern code machine was an ingenious leap in cipher technology, which was the first time electrical circuitry was used in a cipher device. Despite its failure to gain market acceptance, it had far-reaching historical significance during World War II. Unfortunately for the enigmatic Edward Hebern, his contributions were not recognized or rewarded in his lifetime.

Edward Hebern
Patent for Hebern one-rotor cipher machine
with attached typewriter

In 1908, Edward Hebern was in jail for stealing a horse. He claims this gave him time to come up with several cipher-related inventions, which he patented, starting in 1912. In 1917 he came up with the idea to have an electric rotor scramble the alphabet and made his first prototype device. In 1918 and 1919, three other inventors in Europe would come up with the same idea, including Arthur Scherbius, inventor of the infamous German Enigma machine, which you can also see at the Computer History Museum.

The timing of this electric rotor innovation was significant. The Hebern code machine was invented in the middle of World War I and the need for a strong, but easy-to-use cipher device was made especially obvious during this war. The reason for this dire need of new cipher methods was because WWI was the first major war in which the new invention of the radio played such an important role.

The radio changed modern warfare by giving commanders immediate communications to their troops to conduct battlefield strategy. But using the radio meant all communications were intercepted by the enemy. After the end of WW1, every country involved was shocked to find that their ciphers were broken by the enemy! The antiquated, manual cipher methods used for hundreds of years would no longer work.

The Hebern cipher machine looks like a small typewriter with 26 letters that light up, instead of printing on paper. The rotor is on top of the machine and scrambles the electrical signal going between the letters of the keyboard and the light panel. When each letter is typed, the rotor will rotate one space giving a new scrambling sequence. This scrambling sequence repeats after 26 letters of the message, so this was a relatively weak cipher, but equivalent to the types of ciphers in use at the time.

To decipher a message, the rotor is taken out of the machine and put in backwards. The encrypted message is typed in and the plaintext message will then appear on the light panel. The huge advantage was this made the Hebern a machine cipher rather than a manual cipher, which was user-friendly and not prone to human errors. Later, Hebern would introduce a 3-rotor and 5-rotor cipher machine, greatly increasing the strength of the cipher while keeping the ease-of-use features.

Wiring of the single rotor, note that the rotor is removed and inserted backwards to decode the message

The Hebern device in the Computer History Museum is the very first version, the one-rotor model which has a serial number of 10. Today, there are only 12 known Hebern devices in existence, 5 which have the single rotor, one with 3 rotors, and the last 6 devices have 5 rotors.

Edward Hebern had high aspirations for his invention and was also a skilled marketing promoter. By 1921, he incorporated the Hebern Electric Code Company, selling $1 million dollars in shares. He built a beautiful and extravagant gothic-inspired factory in Oakland, California for $386,000, designed for 1,500 employees.

Hebern Electric Code Company factory in Oakland, California

Edward Hebern was better at marketing his idea and his company rather than his invention. Just like Arthur Scherbius and the Enigma machine, Hebern had few commercial companies interested in his new invention. In 1925, he sold a few of his 5-rotor devices to the US Army and Navy for evaluation purposes. The Navy went on to purchase 36 more over the next 6 years and tried to convince the Army to use the same machines so they could exchange messages. What happens next is a story of intrigue and espionage worthy of a spy thriller.

Ode to the Hebern Cipher Machine

Marvelous invention comes out of the West
Triumph of patience, long years without rest
Solved problem of ages, deeper than thought
A code of perfection a wonder, is wrought

Of international scope, is the code electric
With merit so obvious, no nation can reject it
Result of deep study, when necessity goads
Hebern Electric, is the peer of all codes

Sphinx of the wireless, guardian of treasure
Brain of a nation, safety beyond measure
Heart of a battleship, preserver of lives
When brute force, against intellect strives

Keeper of secrets, of state and alliance
Inscrutable, wonderful, a mystery to science
Of depth so profound, brainy traitors, beware
Invisible around you, is the genii's snare

Conceived of the world war, in desperate need
Brains of all nations, competing in speed
Trained minds of the highest, seeking for might
An American achievement, is now brought to light

The US Army never purchased any more Hebern devices and, in fact, blackballed these devices for use by the US military. The reason is the legendary US cryptanalyst, William F. Friedman, successfully broke the 5-rotor Hebern code machine! The 5 rotors of this machine would rotate just like the Enigma machine, which was in odometer fashion, so the Enigma machine also fell victim to Friedman's codebreaking skills. Even though this type of regular motion was exploited by Friedman to break the Hebern and Engima machines, the US military did not tell Hebern, so they could use this knowledge to break any other similar cipher machine.

The German military must have understood the weakness of regular rotor movements also, since they added the plugboard to their Enigma machine in 1930. The plugboard added more brute cryptologic strength to the Enigma than the rest of the machine combined. The method used to break the Enigma during WWII was to separate the breaking of the rotors from the plugboard, so knowledge of codebreaking the regular rotor movements of the Enigma was still exploited.

Hebern never knew why his machine was not adopted by the US military and would end up selling fewer than 100 machines. His factory never got into full production and Hebern ended up back in jail for defrauding his investors.

Meanwhile, with the knowledge gained from breaking the Hebern, William Friedman with Frank Rowlett, invented an electric rotor cipher machine that would not have regular rotor movements, which was called the SIGABA. This device used 10 rotors to scramble the alphabet, with another 5 to cause irregular stepping of the 10 rotors. This was used for high level messages in WWII and was never broken by the enemy.

No doubt, if Hebern knew of this "odometer-stepping" vulnerability, he could have designed a machine similar to the SIGABA, but then our enemies would also be in on the secret. Keeping this secret in the mid-1920s allowed the US to have a secure cipher during WWII and to go on to exploit other cipher devices, like the Enigma machine, for many decades.

Friedman and Rowlett would also gain fame in breaking the Japanese Purple cipher just before WWII, never having the advantage of seeing the machine or speaking Japanese. Friedman would go on to further cryptologic intrigue by travelling to Switzerland in the 1950s to make a deal with Crypto AG for the US to have a secret back door into their cipher machine, which was used by over 100 countries and exploited by the US for the next 4 decades!

Edward Hebern, despite his genius and marketing prowess, never received the recognition he deserved for his brilliant invention. His code machine was the world's first cipher device to use electricity to encode a message. It was also the catalyst for the US to have secure communications during WWII and to exploit the weakness of other cipher devices using regular rotor movements. Hebern's code machine was at the forefront of bringing the world into the era of the machine cipher and the first salvos of crypto warfare.

Copyright © 2016 by Ralph Simpson - Creative Commons Attribution-ShareAlike 4.0 International License