On July 15, 1928, the Enigma machine encoded its first message, setting the stage for encrypted German communications and secret heroism at Bletchley Park during World War II. The portable Enigma machine, which looked like a typewriter, offered an astounding 150,000,000,000,000,000,000 combinations thanks to an intricate system of rotor wheels and patch cables.
As long as sender and receiver had the day’s previously agreed-upon key—the arrangement of rotors and plug board connections—encrypting and decrypting messages via Enigma was a simple but time-consuming process. Generally it required two cipher clerks: one to enter the unencrypted message, and another to record the coded results shown on the lamp board. Once enciphered, the coded message was sent by a radio operator for another two-person team on the receiving end to decipher.
Cracking Enigma's code
A team led by Alan Turing at Bletchley Park in England cracked the Enigma’s code. Repeated phrases in intercepted German messages—everything from weather reports to “Heil Hitler!”—provided clues about daily encryption keys. After creating crib sheets with these clues, codebreakers used mathematical algorithms and electronic processing to break the code. Historians estimate that the work of the Bletchley Park codebreakers, which remained a secret for more than 30 years post-World War II, shortened the war by as much as two years.
Changing and transmitting encryption keys every day was an arduous, time-consuming process—and certainly wouldn’t work in modern times, when we need encryption not only for military maneuvers but also for online bill payments, Prime Day shopping, and mobile coffee orders. In 1976, Whitfield Diffie and Martin Hellman, two researchers at Stanford University, published a paper describing “public-key cryptography,” a two-key system that requires a secret private key to unlock a public key. Public key cryptography remains the standard for encryption today and is built into the SSL technology powering online financial transactions. If you’ve used an https:// website, you’ve used public key cryptography. Feel like a spy?
Tech Time Warp is a weekly feature that looks back at interesting moments and milestones in tech history.
Photo: Giorgio Rossi/Shutterstock