Encryption Keys: A Brief and Exciting History

For as long as humans have been using written forms of communication, we’ve been trying to conceal messages in plain sight. From the secret decoder rings in our childhood cereal boxes to the algorithms that keep our credit card information secure online, cryptography has become a fascinating part of our everyday lives.

Code making and breaking has come a long way since the Greeks invented the first encryption tool, but nothing has made a greater impact on keeping data and messages safe than the invention of the encryption key.

Early ciphers were fairly straightforward compared to modern forms of encryption. Julius Caesar famously used a “shift” or substitution cipher to correspond with Roman military generals. This type of cipher, later called a Caesar cipher, involves replacing each letter in a message with a letter several places away in the alphabet.

Example of a Caesar Cipher (Source - public domain)

Substitution ciphers are easy to use and almost as easy to crack. Every letter gets shifted by the same number of spaces, resulting in a fixed pattern. For example, E always equals B, no exceptions, making it easy for readers to notice a pattern just by scanning the message. Once readers figure out two letters in the cipher, they can easily figure out that the author moved each letter forward by three letters in the alphabet. Game over.

The challenge of inventing a code that was both easy to use and tough to decrypt persisted well past the fall of the Roman Empire. Italian cryptographer Giovan Battista Bellaso was the first to describe a code that used a simple encryption key in 1553. Thirty years later, French cryptographer Blaise de Vigenère fully developed the concept, now known as the Vigenère cipher.

In a substitution cipher, the author shifts each letter by the same number of places. With a Vigenère cipher, the author uses an encryption key, typically in the form of a word or short phrase, to determine how many places to shift the letter. For instance, if your key is “AVOCADO,” the first letter in your message is shifted 0 places (corresponding to the “A” in AVOCADO), the second letter is shifted 21 places (matching the “V”), the third letter is shifted 14 places (matching the “O”), and so on. When you run out of letters in the key, you begin again with the letter A and corresponding number of shifts (0).

Vigenère table (Source -- public domain)

The Vigenère table, pictured above, makes the process even easier by showing which letter is the prescribed number of spaces away. The end result of a Vigenère cipher is a highly varied code where B doesn’t always equal E, as it would using a Caesar cipher, so there’s no discernable pattern.

For 200 years, Vigenère ciphers were considered unbreakable. The use of an encryption key, especially if the key was a long and random string of letters, was the main reason why cryptographers couldn’t crack messages written using the cipher. Prussian cryptographer Friedrich Kasiski was the first to do so in the 19th century, followed by British mathematician Charles Babbage.

Modern encryption methods aren’t based on the Vigenère cipher, but the strength of our security methods owes a lot to the use of strong encryption keys. The next frontier in encryption key history has arrived with consumer-managed encryption keys, which give enterprises full control over their encryption without compromising cloud functionality or performance.

Discover how modern enterprises are securing business information in the cloud.