A Practical and Hands-On Intro to Ciphers and Signals for Parents and Kids

Dennis Chow
Mar 19, 2020 · 18 min read

Introduction for Parents and Educators:

There is much discussion around cyber security skills and talent shortages approaching. However, just like the learn2code effort, teaching STEM to kids is not exactly an easy task. Many concepts and hands-on skills are difficult for adults, let alone kids. Cyber and information security has a vast array of knowledge you must master. Cryptography and Signaling is among these skills. Why teach children these skills as opposed to deploying a firewall first? It’s because these skills are used everyday and we see it in movies. This article will briefly cover the use of ciphers for encrypting plain text and decryption as well as the mechanisms (signaling) on delivering plain or cipher encoded messages. For parents that want to provide this information in an hands-on approach using my PowerShell script, please follow along and refer to my github for a copy of the material. The language used in this article have also been simplified so that children can also read along. The recommended grade level to teach this lesson to is 4th grade or higher. Are you ready to take your child’s STEM skills to the next level? Follow the links as well for complementary reading. Read on!

Introduction for Cyber Security / Technical Professionals:

Some of these sections are meant for parents to have meaningful activities teaching their kids signaling/ciphers. So there’s theory and the use of PowerShell through a 2D array ingestion of for the word search. You can skip over some of the theory and go straight to my Github and review the comments for more usage and ideas. You can go directly to the signaling sections for ideas on how to communicate in an obfuscated manner that would be difficult for SIGINT analysis while combining linguistic crypto.

What are Ciphers and why use them?

Ciphers are functions either through a form of math formulas or some other form of methods that can be repeated through steps. Ciphers are a small part of the world of cryptography where the primary goal is to hide messages or communications from people you don’t want to know what you’re saying. It also means you only want your messages to only be understood by your intended friend. Ciphers also reveal or unlock hidden messages through a key, something only you and your friend know. Someone without he key cannot unlock the hidden message. As illustrated below, you take the method or steps you want to use to hide or encrypt the message and combine it with as secret (your key). Now the message becomes unreadable until your friend uses that same key to unlock or decrypt that the message:

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What is signaling and how are signals used?

Signals are any representation that “means” something to you or someone. For instance, speaking to someone; the set of noises and gestures you may make with face and hands all form one or more signals to your friend you’re speaking to. When you write a message on a piece of paper and hand it to your friend, you are sending a signal, and your friend is receiving a signal. The signal is the piece of paper that transfers your message to your friend. You could send a different signal for the next message you want to send through by saying your message to your friend. If you write a letter to your friend, that’s one signal. If you want to walk up to your friend and tell your friend something else or the same thing, that’s another signal. Two distinct signals.

Putting it together: Using Word Search Puzzles for Crypto and Communicating Signals

Let’s get hands-on with using ciphers and signals to communicate those hidden messages to our friend(s). Do you remember how a word-search puzzle works? You find words in a scrambled set of letters to reveal the messages someone wants you to solve. The following illustration is an example of a 15x15 square of letters with the followings that I may want to send to my friends! But before you go “solving” the word search puzzle; I want to communicate the phrase “change security” to my friend. But how do I hide it from anyone else seeing it but my friend?

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The Encryption Cipher of the Word Search Puzzle

Great! We have our components identified of what to use to send our message but how do we convert a word search puzzle into a cipher? We don’t. The word search puzzle is an array of 2-dimensions (2D) is actually is the key you’re going to give to your friend so they also have a copy to decode the message. We’re also not going to “solve” the word search puzzle by circling the words. We’re going to use what’s called substitution and transposition as our cipher. Substitution is when you replace a character (letter) or word with something else in its place. A transposition is when you “shift” or “move” a character or word based on a specific offset interval.

How do we apply substitution and transposition as a cipher to the word search puzzle?

If we look at the word search puzzle as a 15x15 square, we can think of it as quadrant (Quadrant 4 specifically) from a math plane and assign each letter within as coordinate pairs. So the first letter in our puzzle, which appears to be “F” we can think of it as the pair, x=0, y=0 (0,0) because it starts at the first position (0 offset) for both the row and the column in the square. This is illustrated below:

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Extended Signaling and Cipher Concepts *Recommended for Grades 7 and above

By now you should have been able to successfully use symmetric crypto methods for encrypting and decrypting basic communications using a cipher, key, and plain text. We also discussed the idea of signaling which could include different mediums or channels by which your plain text, key, or encrypted text could be passed to a friend. What if you wanted to add on to this concept and further add complexity to your signaling. In a word-search puzzle, couldn’t the shape be something other than a square? Couldn’t it be a circle or triangle? When you utilize encrypted communications typically there are rotations that happen where the the friends communicating could change any of the following:

  • Cipher for encryption/decryption routines: (e.g. instead 1–1 coordinate matching to letters, what if you added a function of 2x+k where X is the plain text value substituted as an number (remember our discussion on Caesar ciphers?) and K is the key, where you could use any number). The output would be encrypted numbers that correspond to letters. For decryption you would use the inverse which would be the inverse function (k — x / 2) .
  • The key or shared secret (e.g. Changing the size of the key, shape and selecting coordinates or letters)

Alternative Signaling and Key Changes

The previous section(s) are about using common dialog that friends and people generally interact with each other. Signals can be sent over different mediums and meanings in more obfuscated ways. Have you ever thought about how radio and sound work? Sound travels in varying waves and frequencies. Different representations such as sine vs. square “wave” changes in sound and shape. In our example, we can apply a change in our signal representation to tell someone that the next key is going to be in the shape of a 15 x 15 square without actually speaking it in words. Your friend would already have to know the signal protocol which are a set of known “rules” for you both to communicate. You wouldn’t necessarily communicate whole encrypted text messages to each other, but you will establish symbolic meaning using signals to share with each other the components of your secure communication (key, cipher, and encrypted text).

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Changing the Cipher Function

In our previous examples, we have utilized the coordinate presentation as our system or steps to be our cipher for encryption and decryption routines in our secure communication. We can also easily implement substitution only cipher in the same symmetric key method. Our last method focused entirely on representing a geometric shape and the positions of each letter based on row and column. We can also use a simple math formula of (2x+k) which would be our encrypting cipher function and (k-x/2). X is our plain-text letter that represents a substituted character in the alphabet (could be 1–26) and K is our key.

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Wrap-Up Extra Learning and Challenges

I hope this was a fun and exciting way for parents to actively be a part of their child’s learning within STEM. We have gone over some basic core concepts on what are signals, ciphers, and how to apply them using multi-dimensional arrays. For those of you with older children, the extended section reinforces the concepts of cipher use by changing components within the secure communication. Using symmetric key encryption methods, individuals can utilized pre-shared protocols, ciphers, and keys to create their own custom secure communication. We also learned that when you rotate or change any component of the secure communication that there is overhead on outside parties attempting to break or crack your secure communication.

Extra Challenge:

Using any combination of the above methods, can you think of a completely different signal, cipher, and key representation combination that could be used to established secure communications? Perhaps using 3-dimensional key spaces or a different signal protocol? Don’t forget to try making your own word search puzzles for additional practice found at the Discovery Education Channel site.

Feedback:

I’m very much open to feedback if this or did not work for helping your child learn crypto and signaling. Please feel free to share or comment on how it helped or didn’t help you. For those of you interested in cyber security and need services or products for your company or home, feel free to drop us a line at www.scissecurity.com We provide full cyber security stack solutions and utilize our own STEM skills to incorporate machine learning and other predictive analytics in hunting for threats within your environment.

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