Secret notes can be a fun way to communicate with friends without being read by unauthorized persons. There are many encryptions and methods that can be used to create truly unbreakable messages. Whether you intend to send a love letter or a secret message, using a secret note will keep your message safely in the hands of the intended recipient.
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Method 1 of 4: Creating Substitution Encryption
Step 1. Replace the letter with another letter
In the case of simple substitution encryption, you can assign the value of one letter to another. For example, A might equal C and F equal J. Make sure you don't choose too easy a combination like A=B or A=Z. This encryption is easy to crack.
- Make a decoder ring. The set-top box that came in the cereal box a few years ago might come in handy now, but you can also make your own if you want. Write the letters from A to Z, in large circles. Then, write the substitution letters inside the big circle so that they form their own small circle. Now you have the encryption key.
- Random encryption. After you and the friend you want to communicate with have each other's keys, cut out the two rings from paper. Twist the small ring inside the larger outer ring to make a new substitution. When you send a letter, write down what A corresponds to and the recipient will know how to arrange the two rings.
Step 2. Replace the letters with homemade symbols
To make the encryption a little more complicated, you can create a simple, homemade symbol to replace the letters. The more different the symbol from the letter it represents, the more difficult the code will be to crack. Make symbols that are simple and easy to draw.
- Create a key for your new language. Create a primary key that indicates which letter will represent which symbol. As you practice writing with new symbols, you'll get used to them, but at first you'll need a key to remember the letters each symbol represents.
- Share keys with friends. Your new language is useless if you are the only one who can read the letter! Share the keys with friends and ask them to keep it in a safe place so that no one else can find and study the symbols.
- Write your message in a new language. Practice writing with new symbols until you can read and write them as fast as your native language. You may need some time to practice, but over time you will get used to it.
Step 3. Substitute letters from other languages
For example, replace A with (α) Alpha, B with (β) Beta, C (with (X) Chi, and so on from the Greek alphabet.
- Use similar characters for missing letters. Some foreign alphabets may not have all the letters needed in your language. Greek doesn't have a Y, but Upsilon (capital Y) has a similar visual. So you can use it instead. Make sure the recipient of the message knows that you will be replacing some letters with letters that are not in the language.
- Do some tests. For example, “Tonight” becomes “this Mαλαμ” by replacing the letters of the Latin alphabet with the Greek alphabet.
Step 4. Replace numbers with equations
Numbers tend to stand out among text sets. So you have to find a way to hide it better. For example, you could replace the “8” in the message “Tonight, 8 o'clock” with “√(128/2)”. The number 8 is replaced by a simple mathematical equation: the square root of (128/2=64)=8.
Step 5. Know that substitution encryption is unbreakable
It's fairly easy to decode substitutions because you're sticking with the original language and just replacing it with another letter or symbol. Words like “and”, “you”, and “who” will appear frequently in your messages, and can be found and used to piece together key pieces. Some common letters like E, T, and A also help the code breaker to translate your message.
Method 2 of 4: Using Transposition Encryption
Step 1. Use simple transposition encryption
Transposition codes alter normal messages by rearranging letters according to mutually agreed rules. This kind of encryption can be more difficult to crack than substitution encryption because you won't find words that appear frequently. All will be randomized.
- Write messages normally. Since you'll be shuffling messages, you'll need normal messages as a starting point. Choose something simple to start with, like “How are you?”
- Decide how you will rearrange the letters. One example of transposition encryption is arranging each letter in a word, not a sentence, in reverse order. "How are you?" will be “What rabak?.
- Tell your friends how to rearrange the words. They need to know how you scramble the words so they can rearrange the message and read it. Choose a more complicated method than simply putting the words in reverse because “What rabak?” too easy to solve.
- Try using a matrix. Draw a large square on a piece of paper and divide it into equal rows and columns. Write a normal message with one letter in each of the smaller boxes. Your new message will be created by making vertical columns into sentences, not sentences written horizontally. To decode, you have to have your own grid, write sentences vertically, then read them from left to right normally.
Step 2. Use the snake method
This technique is one of transposition encryption because the letters are written and arranged from top to bottom on a sheet of paper, not from left to right, thus creating blocks of text. Be aware that this encryption may be easy to crack as the words are not scrambled.
- Write the message starting from one corner of the paper. Draw the column up or down from the starting point. Write in a straight line to the other side of the paper.
- Use the next column when you reach the edge of the paper. Once you reach the edge of the first column, start writing the next row in the opposite direction. If you started writing from the bottom left corner, you will now write following the line down towards the next edge of the paper.
- Repeat for each column. Keep writing messages up and down, like a snake. If someone else looked at it, he would just see a block of text that made no sense when read from left to right.
- Sign the letter by drawing a small snake. Your friends will know the technique used and how to read the message. Meanwhile, others will not understand it.
Method 3 of 4: Creating Text-Based Encryption
Step 1. Use snippet of text encryption
Choose short text fragments and make sure each letter in the alphabet is used at the beginning of the words in the fragment. If it's too difficult to find fragments with words starting with X and Y, you can write your own snippets of text.
- Number each word. Start with the first word in the text, count the words and number them from left to right. The result will look something like this: “Today1 today2 I3 planning4 going5 to 6 mal7…”, and so on.
- Write your message using these numbers. Using the example above, you would get: H=1, I=2, A=3, B=4, P=5, K=6 and M=7. To spell the word "what", you would write 353.
- Share that piece of text with friends. Don't be numbered and ask them to silently count the letters. To others, that snippet of text will look like a regular paragraph, not a key to cracking the code and no one will suspect anything.
Step 2. Use book encryption
Like encrypting chunks of text, you'll use the words in the book to make up the words in the message you're sending. You will create rules that determine how to find words and use them to convey messages.
- Select the book to use. You can choose any book, but make sure the recipient of the message also has the same book. Books must be from the same edition so that the words and pages are exactly the same.
- Define method. Book encryption often uses three digits separated by commas to mark information. The code (100, 28, 5) can indicate that the word you are looking for is on page 100, line 25, and the fifth word from the left.
- Write your message using this method. Your “words” will be arranged in groups of numbers and are nearly impossible to decipher. Book encryption is very difficult to crack because in order to do so someone has to know and have the exact same edition of the book you are using.
Method 4 of 4: Creating a Hidden Message
Step 1. Make invisible ink with lemon
You can make the ink invisible using lemon juice and water. Lemon juice looks transparent when spread on paper, but turns brown when heated as it oxidizes. This method makes it easier for you to convey a secret message because no one will suspect you are writing on paper.
- Squeeze half a lemon in a small bowl and mix it with a few drops of water.
- Use a brush to apply lemon juice to the paper, just like normal writing. Do not use too much liquid as the paper will get wet and tear.
- To decode, you can heat the paper with a hairdryer or hold it near a warm light bulb. The transparent lemon juice will slowly turn brown when heated.
Step 2. Make invisible ink with cornstarch
This invisible ink requires more ingredients than lemon juice ink, but if you have cornstarch and iodine available at home, you can make one. You will also need a stove.
- Combine 2 tablespoons cornstarch and 4 tablespoons water in a small saucepan.
- Heat the mixture over the stove over medium heat until it is warm, not hot. It takes about 3-4 minutes.
- Dip a toothpick into the cornstarch mixture and use it to write messages. When dry the mixture will be transparent so it looks like a plain blank sheet of paper.
- Here's how to make a solution for reading messages: Mix 1 teaspoon of iodine with 10 tablespoons of water in a bowl. Stir until well blended.
- Dip a sponge in the iodine solution, wring it out to remove excess liquid. Carefully run the sponge over the paper to read the message. The text will turn purple. Be careful not to get the paper too wet!
Step 3. Make a small white board
This method does not essentially generate hidden messages, but allows the recipient of the message to delete them quickly and easily. In this way, the message will be safe from the eyes of curious people and provide a certain level of security. You will need glossy tape, small card paper or paper and liquid pen/marker.
- Cover the card or paper with masking tape. Make sure you choose a glossy tape, such as duct tape, not an "invisible" opaque tape.
- Write a message on the tape with a marker.
- Send a card to a friend. The card will look like a normal letter (plain paper written with colored markers).
- Your friends can now erase messages written with a liquid pen from the surface of the tape and destroy secret messages once they are read.
Tips
- Try not to use spaces in the code. When you use spaces, it's easier to find words that occur frequently and use their meanings to decipher the entire message.
- Make sure your letter reaches the right people. Being careful when sending mail can help secure the code. Even if other people can't read the letter they intercepted, it's possible they're curious enough to try to crack the code.
- Don't forget to give the keys to your friends! Give him the key before you message him so he can crack the code you sent him and have enough time to practice. No matter what encryption method you use, there is always a way to generate the key.
- Keep the keys in a safe place. Make sure you and your friends keep the keys in a safe place. It would be even better if everyone memorized the keys and then destroyed them after enough practice.
- The safest way to store keys is to memorize them, after which you can discard or delete them. This way, only you and your friends will understand the message in the letter.
Warning
- Be careful when exchanging messages in class. Even if it's encrypted, teachers can still get mad if they see you doing it and you could get in trouble.
- Never use code to write anything illegal! Even if you think it's 100% secure, there are many government agencies tasked with finding and cracking code they find suspicious.
