A Beginner's Guide to Cipher Solving

written by Vivian Murphy

An Introduction to Cryptography

To put it simply, Cryptography is the study of hiding and revealing messages, or more broadly any kind of information. We call the tools of the trade "ciphers," and people have used it to play hide and seek with information for thousands of years. With the advent of our modern age, though, computers have caused these tools to become rapidly more complex for usage on the internet and to keep your data secure.

Throughout history, cryptography has been an essential part of diplomacy, statecraft, and war. In the classical times of Greece and Rome, ciphers were simple and mostly involved modifying or rearranging the letters of a message (often called "substitution") with a key of some sort, which differed based on the type of cipher used. This principle of a "key" known only by the sender and recipient often makes up the base of modern ciphers as well. So, when it comes to trying to solve a cipher, to literally "de-cipher" it, you have to be the one to find the key.

Before computers came along, ciphers were simpler and easier for you and me to comprehend. Here's a list of a few of some of the big ones that I think you should know of:

The Caesar Cipher: Each letter in the message is shifted forward a number of places in the alphabet equal to the key.

The Polybius Square: For which this zine is named, it takes a 5 by 5 square grid filled with the letters of the alphabet in random spaces, and then the letters of the alphabet become two digit numbers based on the (x, y) coordinate of the letter.

The Vigenere Cipher: Similar to the Caesar cipher, it instead uses a word as the key. Each letter in the message is shifted forward in the alphabet a number of places in the alphabet equal to position of the corresponding letter in the key's position in the alphabet. This one's super complicated, and we'll come back to it later in more detail.

Morse Code: Not a true cipher, but it still hides every letter in its message behind dashes and dots (or long and short electrical signals).

Other methods of encryption and decryption exist, too, such as using lemon juice. So long as it deals with being able to hide and reveal a message, it's cryptography!

The computer's invention came down to needing a machine that could do unthinkable amounts of math very quickly. The point of doing this math was in order to create more difficult ciphers--and also to break them! Famous is the work of the British Bletchley Park in WW2, which used the help of early computing power to crack the powerful German Enigma machine. Since then, computers have become much stronger, and their abilities to effectively and quickly encrypt, decrypt, and even brute force, have risen exponentially.

Cracking cipher codes has even become a hobby for some, and online communities have even birthed the 'Alternate Reality Game,' or ARG, in which puzzles are placed for people to solve--many of which are created using cryptography, trying to hide the solution behind ever more creative, interesting, and even strange uses of ciphers and encryption.

However, before we start learning in-depth about a few specific ciphers, there are a few bits of terminology that will be helpful for explaining ciphers. So, here's some vocabulary to help you out for the rest of this article:

Cipher: A method of encrypting and decrypting information. (Ex. Caesar cipher)

Encrypt and Decrypt: To encrypt information is to put it into a cipher or other means of concealment to hide it. Decrypting information is the same, instead it works to reveal the information.

Key: Some sort of input which is used to encrypt and decrypt information, usually in a cipher. Typically, keys are strings of numbers or letters. Keys are typically kept hidden, as they are used to solve a cipher.

Plaintext: A message, typically text, which has not been put through a cipher.

Ciphertext: Any message which has been put through a cipher in order to conceal its information, also known as encrypted data.

Cryptography: The study of ciphers, solving them, creating them, and judging their effectiveness and efficiency.

Solving Ciphers: Caesar, Polybius, and Vigenere

There are three ciphers I'd like to take us through today. They're all fairly introductory and should be fairly simple to wrap your head around. After I explain one cipher, I'll give an example for you to solve on your own before you advance to the more difficult cipher.

Let's start with what is generally considered the simplest cipher, the Caesar cipher. In practice, it's fairly easy to wrap your head around, but it can still be difficult to crack if you aren't given the key. The Caesar cipher works by putting all the letters through a simple key, which is a number. From there, you move every letter forward in the alphabet as many times as the key states. For example, when the key = 4, L becomes P; when key = 20, D becomes X. Additionally, when the key moves forward a position that would be over the end of the alphabet, you start over from the beginning of the alphabet, for example, key = 4, Z = D.

To decrypt a Caesar cipher, move all the letters backwards based on the key, reversing the sequence used before. Even as the simplest cipher, it can still be difficult to decrypt if you don't have the key. My personal advice is, first and foremost, to locate stretches of words that have repeating letters, such as "creek." From there, make a guess on what letter those two have been transformed from, say we have "lannt," we might think that that ‘n' is actually an ‘e.' Then try the rest of the word and move the other letters back nine. Second, look for any special punctuation, especially contractions. Expert cryptographers won't include punctuation in order to trip you up. Lastly, think about sentence context. If you know what situation the encrypted message is covering, you might be able to guess a word and crack it that way.

I understand that's a lot of information to throw your way, but now you try. I won't give you the key, so you'll have to figure it out on your own. Use the tricks I gave you above! Try not to use any online hints or cipher solvers unless you get stuck. When you think you're right, type your answer into the text box below, and if you are, you'll be taken to the next stage.