Encryption is what keeps your personal data secure when you're shopping or banking online. It scrambles data like your credit card details and home address to ensure hackers can't misuse this information.
Today, encryption involves powerful computers and some equally powerful brains.
But it wasn't always so complicated...
Ancient Spartan technology
Circa 600 BC: The ancient Spartans used a device called a scytale to send secret messages during battle. This device consists of a leather strap wrapped around a wooden rod. The letters on the leather strip are meaningless when it's unwrapped, and only if the recipient has the correctly sized rod does the message make sense.
Roman encryption and ciphers
Circa 60 BC: Julius Caesar invents a substitution cipher that shifts characters by three places: A becomes D, B becomes E, and so on.
1553: Giovan Battista Bellaso envisions the first cipher to use a proper encryption key - an agreed-upon keyword that the recipient needs to know if he or she wants to decode the message.
1854: Charles Wheatstone invents the Playfair Cipher, which encrypts pairs of letters instead of single ones and is, therefore, harder to crack.
1917: An American, Edward Hebern, invents the electro-mechanical machine in which the key is embedded in a rotating disc. It's the first example of a rotor machine. It encodes a substitution table that is changed every time a new character is typed.
1918: German engineer Arthur Scherbius invents the Enigma machine (pictured) for commercial use. Rather than the one rotor used by Hebern's device, it uses several. Recognizing its genius, the German military begins to use it to send coded transmissions.
But wait. There's more about Enigma.
1932: Polish cryptographer Marian Rejewski discovers how Enigma works. In 1939, Poland shared this information with the French and British intelligence services, allowing cryptographers like Alan Turing to figure out how to crack the key, which changes daily. It proves crucial to the Allies' World War II victory. You can read more about the Bombe Machine designed by Turing and created by the British Tabulating Machine Company here.
1945: Claude E. Shannon of Bell Labs publishes an article called "A mathematical theory of cryptography." It's the starting point of modern cryptography.
The early 1970s: IBM forms a 'crypto group,' which designs a block cipher to protect its customers' data. In 1973, the US adopted it as a national standard - the Data Encryption Standard, or DES. It remains in use until it cracked in 1997.
2000: the Advanced Encryption Standard replaces DES, or AES, found through a competition open to the public. Today, AES is available royalty-free worldwide and is approved for use in classified US government information.
Today: As more and more services move to the cloud, encrypting data in transit is crucial, and cryptographers are continually developing and refining solutions to this challenge.
Related content: A brief history of pioneering women in technology