9 Times People Broke Unbreakable Codes - And How

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Vote up the most ingenious code breakers in history.

For all of history, humans have enjoyed a good puzzle. Puzzles, codes, and ciphers have been found almost everywhere, from second-century Egypt to the 17th-century letters between King Charles I and Queen Henrietta-Maria. Still today, crossword puzzles, Rubik's cubes, and Sudoku all remain enjoyable ways to pass the time.

But not all puzzles are simply meant for fun and leisure. Ciphers and codes are, of course, also a great way to keep a secret, such as where one buried some hidden treasure. A well-crafted code can also inform your own military of certain movements and plans, and without revealing that information to an enemy. Many of the strongest ciphers and codes endured for decades or even centuries before finally being cracked. The following codes were called impossible, even unbreakable - until the right people came along. 


  • Alan Turing Likely Saved Millions Cracking Codes During WWII
    Photo: Unknown / Wikimedia Commons / Public domain

    Alan Turing was a British mathematician who single-handedly changed the course of history. In September 1939, he took up residence at the headquarters of the British codebreaking team at Bletchley Park. His foe was not just Germany, but Germany's cipher machine called Enigma

    He fought technology with technology and created his own codebreaking machines, which he referred to as various versions of the Bombe. These machines would decipher codes that revealed positions of the dreaded U-boats. In addition, Turing's Bombes would deliver into the hands of the Allies messages sent directly from Hitler.

    Even as Germany advanced their encrypting machines, Turing kept up. His ability to decipher the German codes prevented countless attacks by U-boats (thereby preserving life and crucial supplies), and arguably shortened the length of the war. The BBC estimates that some 14 million more soldiers may have perished during WWII had Enigma not been cracked.

    3,249 votes
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    3,808 VOTES

    Genevieve Grotjan Broke The Japanese 'Purple' Code After The British Gave Up Trying

    Genevieve Grotjan received her bachelor's degree in math and, during WWII, was working in payroll for the government. She was recruited by William Friedman, a cryptanalyst who had a team working on breaking the Japanese "Purple" code. Friedman's team had been working on the task for months with little progress. The British had already given up on trying to crack the code. 

    On September 20, 1940, Grotjan discovered a pattern that would lead to the deciphering of the Purple code. Looking at the encrypted messages, Grotjan noted certain repetitions and cycles that others had missed. When she brought the discovery to the attention of her supervisor, Frank Rowlett, it's been said that he exclaimed, "That's it! That's it! Gene has found what we've been looking for!"

    3,808 votes
  • The Vigenere Cipher Was Considered Unbreakable Before Charles Babbage And Freidrich Kasiski Cracked It
    Photo: Armchair / Wikimedia Commons / CC-BY-SA 4.0
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    1,475 VOTES

    The Vigenere Cipher Was Considered Unbreakable Before Charles Babbage And Freidrich Kasiski Cracked It

    For nearly 300 years, the Vigenere Cipher was considered to be unbreakable by everyone who knew about it. The puzzle uses a combination of 26 different cipher alphabets. Created in 1553, the cipher was cracked in 1854 by Charles Babbage, a British cryptographer.

    Babbage seemed to possess a unique blend of intuition and smarts that allowed him to break the code. He noticed how repetitions in the cipher also translated to repetitions in plain text. Additionally, the space between these repetitions revealed the length of the keyword. However, he never published his work and so the code continued to be considered unbreakable. 

    Fifty years later, Friedrich Kasiski cracked the code and published his work using the same technique as Babbage (although this wasn't known until Babbage's work was finally published later). The method used by both is now referred to as the "Kasiski examination."

    1,475 votes
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    1,005 VOTES

    Deciphering The 3,000-Year-Old Linear B Changed The Study Of Greek History

    In 1878, excavations in Greece undertaken by Minos Kalokairinos revealed a variety of scripts on tablets. One of those scripts was termed Linear B. When it was discovered on the island of Crete, nobody could read it - or even quite knew what language it was. Various scholars tried their hand at deciphering the code, and while progress was made, the code wasn't cracked until Michael Ventris came along in the 1950s. 

    Earlier scholars helped Ventris by classifying the signs of Linear B, and by the construction of a grid showing various relationships between signs. Writing out a variety of grids and using statistical analysis - and some educated guesses - Ventris finally cracked the code.

    He shared his results with John Chadwick, a philologist at Cambridge, who helped confirm the decipher. The two worked together to publish the findings in 1953.

    1,005 votes
  • The Zodiac Killer's Cryptogram Remained A Mystery Until December 2020
    Photo: San Francisco Police Department / Wikimedia Commons / Public domain

    In the late 1960s, the Zodiac Killer terrorized the greater San Francisco Bay Area of California. The identity of the Zodiac Killer and the final tally of his victims is still not known, but one part of the case has finally been solved. The case was notable for the letters that the killer would send to local news outlets as well as live on-air phone calls he would make. 

    After slaying his last (known) victims, the Zodiac sent a cryptogram to The San Francisco Chronicle. The coded puzzle contained 340 characters. The FBI, as well as amateur code-breakers, worked on cracking the code for 50 years. In December 2020, an international team finally succeeded. After realizing it was a transposition cipher, the team simply needed to discover the rules used in the cipher that determined the reorganization of the letters. They then created a software app to help them finish solving the puzzle. 

    Although the cracked code has been confirmed by the FBI as authentic, it does nothing else to reveal any information about Zodiac's potential identity. 

    1,150 votes
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    645 VOTES

    Breaking The 300-Year-Old Copiale Cipher Revealed The Rituals Of A Secret Society

    Containing traditional Roman letters as well as unique symbols, the Copiale Cipher earned its name from one of the few plain text words found on the cipher: copiale. The cipher dates back to around 1770 and was written on green and gold brocade paper. The cipher was hidden in the East Berlin Academy until after the Cold War. 

    An international team of researchers transcribed the text into a version that could be read by a machine. These researchers tried to decode the cipher with the letters from 80 different languages, with no luck. They then realized that the Roman characters in the cipher meant nothing and were simply included to confuse possible codebreakers. They then discovered that the shapes of the symbols held a major key to decoding the text - similar shapes represented the same letter or group of letters.

    This discovery led the researchers to discern that the coded text was German. Once the code was cracked, it became clear that the text belonged to a secret society that called itself the "Oculist Order." The group had a fascination with eyes and eye surgery, and the Copiale cipher revealed the political goals and secret rituals of the society, such as an initiation ceremony that required the prospect to put on glasses and read a blank page. 

    645 votes