How to Invent and Decode Secret Ciphers and Codes

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Send messages only you and your friends can decipher just like a secret agent
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While spies and treasure hunters in movies make cracking codes look super complex, you can actually make your very own secret code or cipher quite easily. No special government training or spy school required. All you need is a bit of creative thinking and a few friends to share the fun with. We’ll teach you everything you need to know about creating codes and ciphers as well as how to read the most common ones. Once you’ve finished reading, start communicating with your friends in your own secret language the next time you see them.

Sample Coded Paragraphs

Things You Should Know

  • Write out words backward so they’re harder to read with just a quick glance. For example, “How are you?” would become “Woh era uoy?”
  • Use color code words for specific situations, such as saying “Code pink!” to your friends when your crush walks in the room.
  • Encipher your messages by replacing each letter you write with the one directly following it in the alphabet. So “Hello” would become “Ifmmp.”
Method 1
Method 1 of 5:

Using Easy Codes & Ciphers for Kids

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  1. This is a simple way of encoding messages so they can't be understood with just a quick glance. A message like "Meet me outside" written in reverse would instead be “Teem em edistuo.” [1]
  2. Write out the letters A through M in a single line on a piece of paper. Directly beneath this line, write out the letters N through Z, also in a single line. Change each letter in your message to the letter directly below or above it in the grid you just made. [2]
    • For example, the letter A would be replaced with N, B with O, C with P, and so on and so forth.
    • By using a reflected alphabet, the message “Hello” would instead become “Uryyb.”
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  3. Draw a tic-tac-toe grid to make a pigpen cipher . Draw a tic-tac-toe grid on a piece of paper and write out the letters A through I in the grid going from the left to right, top to bottom, one letter per box. In this example: [3]
    • The first row is made up of the letters A, B, C.
    • The second row has D, E, F.
    • The last row consists of G, H, I.
  4. Draw another tic-tac-toe grid next to the first one. Fill the grid in with the letters J through R just like how you did with the first grid. Then, draw small dots in each space of the grid as follows: [4]
    • In the first row, starting on the left, place a dot in the lower right corner (letter I), on the bottom side in the middle (letter K), and in the lower left corner (letter L).
    • In the second row, starting on the left, place a dot in the middle of the right side (letter M), in the middle of the bottom side (letter N), and in the middle of the left side (letter O).
    • In the third row, starting on the left, place a dot in the upper right corner (letter P), in the middle of the top side (letter Q), and in the upper left corner (letter R).
  5. The first X will contain the letters S, T, U, and V. In the second X, place dots in the open spaces surrounding where the X crosses so there is a dot on each side of the center of the X. Then, fill in the remaining letters W, X, Y, and Z. [5]
    • In the first (undotted) X shape, write S in the top space, T on the left side, U on the right, and V on the bottom.
    • In the second (dotted) X shape, write W on the top, X on the left side, Y on the right, and Z on the bottom.
  6. The grid shapes (including dots) surrounding the letters are used as substitutes for the letters themselves. Use your pigpen cipher key to translate messages into and out of pigpen. [6]
  7. This might be something with personal significance, or something arbitrary. Write out the date as an unbroken string of numbers. This is going to be your number key, which will be the tool needed by your friend to be able to decode your message. [7]
    • For example, let’s use George Washington's birthday (2/22/1732). The number key would then be 2221732.
    • If you've already agreed to use a date shift cipher with someone, come up with a clue (like “Washington”) you can say to each other to talk about the number key.
  8. Write out your message on a piece of paper. Underneath the message, write out a single digit of the number key for each letter of your message. When you reach the last digit of the number key, repeat the key from the beginning. For example, using George Washington's birthday (2/22/1732): [8]
    • Message : I'm hungry
    • Enciphering :
      I.m.h.u.n.g.r.y
      2.2.2.1.7.3.2.2
      Shift letters forward along the alphabet according to the number key, as in…
    • Coded message : K.O.J.V.U.J.T.A
  9. When you speak Pig Latin , words that start with a consonant sound move that sound to the end of the word and add “ay.” It’s the same for words starting with a cluster of consonants. Words that start with vowels just get “way” or “ay” added to the end of the word. [9]
    • Consonant initial examples: pig = igpay ; me = emay ; too = ootay ; wet = etway ; hello = ellohay
    • Consonant cluster initial examples: glove = oveglay ; shirt = irtshay ; cheers = eerschay
    • Vowel initial examples: ate = ateway ; egg = eggay ; until = untilay ; eat = eatay
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Method 2
Method 2 of 5:

Creating Your Own Code

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  1. Code books can be stolen, lost, or destroyed, and modern technologies and computer programs can oftentimes break even strong, well-planned code. But codes can be used to condense long messages into a single line, making them great time savers. Think about the complexity of the symbols or words you’ll use to make your code stronger and less easy to figure out. [10]
  2. Knowing the purpose of your code from the very start will help you avoid doing any unnecessary work. For example, if your goal is to save time, you might only need a few specific code words or symbols. If you're trying to encode really long and detailed messages, you may need to develop a code book that’s more like a dictionary. [11]
    • Make your codes even more complex by using several different codes in rotation or combination. Just keep in mind that the more codes you use, the more code books you’ll need to make for decoding.
  3. Start by using constrained writing to condense common phrases into a single code word. For example, “Reading you loud and clear” can be a random name like “Roy.” Then, replace words that are especially critical to the subject matter of your message with their own unique code words. Things like names, locations, and actions are best to replace with code words.
    • Write down these code words and their meaning in your code book, kind of like a dictionary.
    • You don’t need to make a code word for every single word in your message. Partially coding what you want to say will be just as effective.
    • For example, the following message replaces just the most important words with code words. In this case, “tango” means “walk,” “restaurant” means “museum,” and “Roy” means “reading you loud and clear.”
      • Message: About yesterday. I wanted to say, Roy . I'll tango to the restaurant as planned. Over and out.
      • Meaning: About yesterday. I wanted to say, reading you loud and clear . I'll walk to the museum as planned. Over and out.
  4. Use the code words in your code book to start encoding messages. Use just a singular code to make it easier to encode your message, or use multiple codes to make it more complex.
  5. Write one letter of the key word under each letter of your message. Repeat the key word until you get to the end of your message. Count how many spaces each letter of your message is away from the letter in the key word. Write this number down and repeat for each letter in your message. The encoded message will be a string of numbers that the recipient will need to decode using the key word. [12]
    • For example, with the key word "SECRET," each letter of your message would convert to the number of letters between it and the corresponding letter of the keyword as you move along the alphabet. One letter of the keyword is assigned to each letter in your message.
    • Keep repeating the keyword until all the letters in your message have a corresponding letter.
      • Message: Hello
      • Encoding:
        /H/ is 11 letters away from the key /S/
        /e/ is the same ( zero ) as the key /E/
        /l/ is 9 letters away from the key /C/
        And so on...
      • Coded Message: 11; 0 ; 9 ; 6 ; 10
  6. As you receive coded messages, refer back to your code book or key to make sense of them. This may take you a bit longer at first, but it’ll become more intuitive as you become more familiar with the code. Soon, you’ll be able to read your code like it’s nothing.
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Method 3
Method 3 of 5:

Learning Commonly Used Codes

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  1. While trying to send messages during a time of political turmoil, Mary, Queen of Scots, used symbols as a substitute code for English letters and common words. View the code by visiting the UK’s National Archives’ cipher website . Some features of Mary's code you might find useful for your own attempts at code-creating include: [13]
    • The use of simple shapes for high frequency letters, like Mary's use of a circle for the letter /A/. This saves time while encoding.
    • Common symbols used as part of the new code language, like Mary's use of "8" as code for the letter "Y." These can confuse code breakers who might interpret this as a number and not a code symbol.
    • Unique symbols for common words. In Mary's day, "pray" and "bearer" received unique symbols, but these were more common then than they are today. Still, using symbols for frequent words and phrases saves time and adds complexity. [14]
  2. Code phrases can pack a lot of meaning into a single phrase. Many kinds of organizations use specific colors to indicate a certain emergency or other situation, such as the DEFCON system, security alerts, and medical alerts. [15] To mimic this system, come up with some colors to use as code words that apply to your everyday life. They also don’t have to be emergency-related.
    • For example, instead of saying "I've got to run to my locker" among your friends, you might use the code word "Code green."
    • To let your friends know that the person you want to date has entered the room, you might say the code phrase, "Code pink!"
  3. Thankfully, books are fairly easy to come by. Using this method, first decide on a book to use as the key to your code. When encoding a message, locate the word you want to send within the book, then send the recipient 3 numbers: the page number, the line number the word is in, and the position of your word within the line starting from the left. [16]
    • Different editions of books might use different page numbers. To ensure the right book is used as a key, include publication information, like edition, year published, and so on with your book key.
    • For example, you might decide on using Frank Herbert's Dune, with the code looking like the following:
      • Encoded Message: 224.10.1 ; 187.15.1 ; 163.1.7 ; 309.4.4
      • Decoded Message: I'm hiding my words.
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Method 4
Method 4 of 5:

Developing Your Own Cipher

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  1. A cipher uses an algorithm, which is like a process or transformation that is applied to a message consistently. This means that anyone who knows the cipher can translate it. On the other hand, ciphers can be a lot more complex than simple code words, and so might keep your messages more secure form regular folks. [17]
    • Many cryptographers add a key, like the date, to strengthen ciphers. This key adjusts the output values by the corresponding number of the day of the month (on the first, all output values would be changed by one). [18]
  2. You can either invent a completely new algorithm, or use an existing one, such as the ROT1 Cipher (also called the Caesar Cipher). This method simply rotates each letter in your message forward by a single letter. [19]
    • ROT1 Message: Hello
    • ROT1 Enciphered: i ; f ; m ; m ; p
    • Caesar Ciphers can be modified to rotate forward by a different number of letters. So you could make it so that you rotate forward 3 letters instead of just one. In this case “Hello” would become k ; h ; o ; o ; r
  3. Add to your algorithm to make it more complex. For example, include a rotating condition to your cipher, like the day of the week. For each day of the week, assign a value, such as 1 through 7. Adjust your cipher by this value when encrypting a message on that day. So on Monday, you shift letters forward by 1. On Tuesday, it’s 2 letters, and so on. [20]
  4. Start deciphering incoming messages that follow your cipher. Reading your cipher over and over will help make the deciphering process a whole lot easier as you gain experience. The great thing about ciphers is that their algorithms are consistent and usually follow some kind of pattern. Getting in the habit of reading ciphers will help you notice trends and crack them a lot faster.
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Method 5
Method 5 of 5:

Studying Common Ciphers

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  1. Master Morse Code . In spite of its name, Morse Code is actually a cipher, not a code. Dots and dashes represent long and short electrical signals which in turn represent the letters of the alphabet. Common letters in Morse, represented as long ( _ ) and short (.) signals, include: [21]
    • R ; S ; T ; L = ._. ; _.. ; _ ; ._..
    • A ; E ; O : ._ ; . ; _ _ _
  2. Many greats in history, like the genius Leonardo da Vinci, have written out messages as they would look reflected in a mirror. Because of this, enciphering in this fashion is often called “mirror writing.” [22] When you write your message, write from right to left instead of left to right, and write each letter backwards.
    • Transposition ciphers generally treat messages or the formation of letters visually. The image of the message is physically transformed into something else to hide its meaning. [23]
  3. Binary is the language of 1's and 0's used by computers. Use a binary alphabet chart to help encipher and decipher your messages. When enciphering your message, be sure to space out each line of binary clearly so the other person knows where one letter ends and the next begins. [24]
    • The name "Matt" would encipher to binary as: 01001101 ; 01000001 ; 01010100 ; 01010100.
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  • Question
    Can I use a secret code generator?
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    This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.
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    Yes, there are a variety of secret code generators. You can use something like a simple cipher wheel, or find a code generator online.
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    What are some famous secret codes?
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    Some of the most famous secret codes in history include the Caesar shift, The Vigenère square, and the Enigma machine.
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    How do you make a cipher wheel?
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    One easy way to do it is to print out a premade cipher wheel template. The cipher wheel consists of 2 circles with the letters of the alphabet written along the outer edges. Place the smaller circle on top of the larger one and fasten them together with a split pin. Turn the inner wheel so that one of the letters lines up with the letter of your choice on the outer wheel (such as Z and C), then pin the wheel in place so you can use the wheel as a guide when writing your cipher!
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      Tips

      • Devise a way to encipher spaces between words as well as the words themselves. This will strengthen your code and make it harder to break. For example, you can use a letter (E, T, A, O, and N work best) instead of a space. These are called nulls.
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      • Learn a different script, such as Runic, and make encryption/decryption keys for those who you want to give messages to. You can find these keys online.
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      • If you want your code to be more secure, create additional symbols for common word endings and beginnings, like '-ing' and 'th-'.
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      References

      1. ↑ https://kidsactivitiesblog.com/27282/secret-codes-to-write-a-coded-letter
      2. ↑ https://www.makeandtakes.com/3-secret-codes-to-try-with-your-kids
      3. ↑ https://kidsactivitiesblog.com/27282/secret-codes-to-write-a-coded-letter
      4. ↑ https://www.civilwarsignals.org/cipher/pigpencipher.html
      5. ↑ https://kidsactivitiesblog.com/27282/secret-codes-to-write-a-coded-letter
      6. ↑ https://www.civilwarsignals.org/cipher/pigpencipher.html
      7. ↑ https://www.math.cornell.edu/~mec/Summer2008/lundell/lecture4.html
      8. ↑ https://www.math.cornell.edu/~mec/Summer2008/lundell/lecture4.html
      9. ↑ https://redtri.com/how-to-speak-pig-latin/
      1. ↑ https://www.khanacademy.org/computing/computer-science/cryptography/ciphers/a/ciphers-vs-codes
      2. ↑ https://www.unmuseum.org/cipher.htm
      3. ↑ https://pi.math.cornell.edu/~mec/Summer2008/lundell/lecture4.html
      4. ↑ https://www.nationalarchives.gov.uk/education/resources/elizabeth-monarchy/ciphers-used-by-mary-queen-of-scots/
      5. ↑ https://asecuritysite.com/coding/mary
      6. ↑ https://www.jointcommission.org/-/media/tjc/documents/resources/emergency-management/em-overhead-emergency-codes-posterpdf.pdf
      7. ↑ http://www.topspysecrets.com/book-cipher.html
      8. ↑ http://www.unmuseum.org/cipher.htm
      9. ↑ https://www.khanacademy.org/computing/computer-science/cryptography/ciphers/a/ciphers-vs-codes
      10. ↑ http://rumkin.com/tools/cipher/caesar.php
      11. ↑ http://www.unmuseum.org/cipher.htm
      12. ↑ http://www.learnmorsecode.com/
      13. ↑ https://www.mos.org/leonardo/activities/mirror-writing
      14. ↑ http://listverse.com/2012/03/13/10-codes-and-ciphers/
      15. ↑ https://www.sciencefriday.com/educational-resources/write-your-name-in-binary-code/

      About This Article

      Article Summary X

      To create a secret code or cipher, start by writing the letters A through M in one row and the letters N through Z in another row underneath. Then, replace each letter in your message with the letter above or below it to encode your message. For example, since the rows give you letter pairs of H and U, E and R, L and Y, and B and O, you’d encode “Hello” as “Uryyb.” Alternatively, use a simple code like writing words in reverse, such as encoding "Meet me later" to "Teem em retal." To learn how to create a pigpen cipher or a date shift cipher, keep reading!

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