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Cipher Tools

Free tools for classical ciphers. They run in your browser, and each one shows how the cipher moves the letters.

Caesar cipher

  • Caesar Cipher

    Encrypt and decrypt with any shift, in several alphabets.

  • Caesar Cipher Wheel

    Turn the disc and follow a message one letter at a time. You can print one to make at home.

Other ciphers

  • Vigenère Cipher

    Shift each letter by a different amount using a keyword, with the key written under your text.

  • ROT13

    The Caesar shift of 13, where the same step encrypts and decrypts.

  • Atbash Cipher

    The alphabet read backwards: A becomes Z and B becomes Y.

  • Substitution Cipher

    Use a shuffled alphabet as the key, and swap letters while you watch their counts.

Breaking a cipher

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Which tool do you need?

If you have a message and a number, use the Caesar cipher tool. A message and a word as the key usually means Vigenère. With no key at all, start with the solver, which tries every shift, and move on to frequency analysis if none of them gives readable text.

Learning how a shift works? The cipher wheel is the slowest and clearest way in. ROT13 and Atbash take no key, so you can paste your text and read the result straight away.

What these tools are for

All of these ciphers can be broken with a pencil or a few lines of code, so use them for learning and puzzles. Anything that has to stay private needs modern encryption such as AES.

Other sections

Cryptography Basics

How ciphers work and where they came from.

Cryptanalysis

How to read a message without the key.

Programming

Tutorials in five languages, an API and a library.