Mad about Science: Ciphers and encryption

By Brenden Bobby
Reader Columnist

Information is the most valuable currency available to humankind. Gold and silver are great, but the information of how to steal someone else’s gold and silver while protecting your own is far more valuable than the resources themselves.

This has been understood by powerful people for as long as we’ve known how to write things down. Being clear and concise in your directives is important, but it’s even more important that your enemies can’t easily read your plans.

The solution for this begins with ciphers. A cipher is a means to disguise or code your written messages to obfuscate information to those outside of the know. The simplest form is a Caesar cipher, named after Julius Caesar, who used them regularly in his written communication.

A Caesar cipher is completed by offsetting a letter a certain number of spaces to substitute it with a new letter. As an example, let’s use a Caesar cipher +3 on the word “soap.”

V is the third letter after S, R is the third letter after O, D is the third letter after A and S is the third letter after P, so your coded cipher becomes “vrds,” which looks like gibberish.

That being said, Caesar ciphers are so commonplace that using very simple logic or a prebuilt graph can make deciphering super simple — barely an inconvenience.

What about encrypting numbers?

A Caesar cipher handles changing numbers a little differently than you might expect. Rather than adding to a number such as 7, you’re instead converting it into a Roman numeral and then shifting those letters. In this case, 7 is VII which becomes ZLL.

In some instances, the principle of a Caesar cipher is used at its core; but, instead of shifting to letters in the pre-existing alphabet, a user will convert them into letters or symbols of a constructed language such as Tolkien’s Elvish. 

As Elvish isn’t a perfect one-to-one match for English, this can create a unique challenge to someone seeking to break your cipher. Additionally, placing another layer of protection by creating a numerical shift or offset can make things more complicated for prying eyes.

This form of cipher — similar to virtually every other form of cryptography — suffers from one major weakness: human pattern recognition. Humans are very adept at recognizing patterns, and particularly in a visual format such as writing. As soon as someone discovers a pattern in your text, it becomes very easy to decipher the rest of the message.

Ultimately all patterns can be identified and broken using mathematical processes.

This was made abundantly clear when the Allies cracked the Enigma machine in World War II.

Invented by German engineer Arthur Scherbius in 1918, the Enigma machine was essentially a typewriter with a set of rotors, a plug board and each letter of the alphabet with a light behind it.

The Enigma machine was simplistic compared to modern encryption techniques, but it was still an extremely complicated device. Operators were sent code books every month with values that would shift every day to keep messages secure. Aside from the rotors scrambling letters on input, the plugs would allow users to swap letters, such as A/P so that any input of A would actually be the letter P and vice versa. In this instance, if you typed the word “APPLE” it would appear as “PAALE.”

The complexity was compounded by the configuration of the three rotors, each of which had the full 26-letter alphabet on them. All components together allowed for more than 158 quintillion different ways you could set the machine to encrypt messages, which changed on a daily basis. 

Sounds unbreakable, right? It wasn’t.

The Allies discovered a few key elements to cracking the code without codebooks or even using an Enigma machine themselves. The first was that the Nazis always started their messages with a weather report. Identifying words such as “rain” helped break a huge chunk of the code. Second, they reliably ended messages with the phrase, “Heil Hitler,” which gave Allies even more of an insight to the overall code.

Another major component and a critical flaw of Enigma was that a letter could never be encoded as itself. Pairing this with the previous information allowed codebreakers to decipher and disseminate information very efficiently.

Another key development was the Bombe machine, a very early computer developed by Alan Turing and Gordon Welchman. This computer was basically 36 Enigma machines put together. The machine employed a tactic similar to a technique used by modern cyber criminals called “brute forcing.”

Have you ever seen a TV show in which someone tries to guess a password by starting with 0000, then 0001? This is brute forcing, but a computer does it many millions of times per second.

The Bombe machine would assume the position of a plug, such as A/P, and another plug would be set to B/K, as an example. It would run all possibilities until it ran into a contradiction where A and P could not be swapped, and would switch to a different plug pair.

It was able to do this very quickly, slamming through all 158 quintillion possibilities in about 20 minutes.

This device is essentially the basis for all encryption we use today. We have vastly more processing power than Turing did in the 1940s, which has allowed for vastly more complicated encryption.

In the simplest terms, encryption is using layers of math to switch letters into other letters. Decryption is throwing the same kind of math many times over until a pattern is recognized. Cryptography is a very complicated process and simplifying it in that way really doesn’t do it justice. If this subject has piqued your interest, consider stopping by the library’s nonfiction section at 652.8 and see if you can discover a book that does a considerably better job at describing the process than I have.

Vwdc fxulrxv, ZLLE