Secret Code and Encryption Playground
Learn how substitution ciphers turn plain text into cipher text using a key, why longer keys are harder to crack, and how letter frequency can break simple codes.
Before you try
What if everyone knew the method but not the key? Would your message still be safe?
Try it out
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What happened?
Move a control to see what changes and why.
These ciphers are centuries old and easy to crack. Messages today are protected by far harder maths.
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Try these ideas
- Encrypt your name with shift 3, then decrypt it with shift −3.
- Try to crack the sample message using the frequency chart.
- Which cipher keeps the letter frequencies most hidden?
Why it works
Encryption scrambles a message so only someone with the key can read it. The Caesar cipher shifts every letter by the same amount (Julius Caesar used a shift of 3). Atbash flips the alphabet (A↔Z). A keyword cipher builds a jumbled alphabet from a secret word.
Type a message, pick a cipher and a key, and watch the cipher wheel and the result update as you type. The frequency chart shows how the most common letters (like E and T) leak through simple ciphers, the clue code-breakers use.
Check your understanding
Question 1 of 3
Using a Caesar shift of 3, the word CAT becomes…
In the Atbash cipher, the letter A becomes…
Why is a Caesar cipher easy to crack?
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Send each other secret notes using a shared key.
- Ask: why should passwords be long and not a dictionary word?
- Discuss why real websites use keys with hundreds of digits.