Keyed Caesar cipher

The keyed Caesar cipher is a variant of the Caesar Cipher that provides increased protection. Instead of having all letters in alphabetical order, it starts with a code word (the encryption key). Unused letters are then added after the code word. If the code word is blank, it behaves exactly like an ordinary Caesar Cipher.

Keyed Caesar Cipher Tool

You must enter the message.

You must enter the encryption key.
You must enter the encryption key.

Auto Solve Options


You can decode (decrypt) or encode (encrypt) your message with your key. If you don't have any key, you can try to auto solve (break) your cipher.

  • Language: The language determines the letters and statistics used for decoding, encoding and auto solving.
  • Iterations: The more iterations, the more time will be spent when auto solving a cipher.
  • Max Results: This is the maximum number of results you will get from auto solving.
  • Spacing Mode: This is about the spaces (word breaks) in the text. In most cases it should be set to Automatic. In case a specific letter (for instance X) is used as word separator, set it to Substitute.


Not seeing the correct result? Try Auto Solve or use the Cipher Identifier Tool.

Auto Solve results

Score Key Text

Still not seeing the correct result? Then try experimenting with the Auto Solve settings or use the Cipher Identifier Tool.


  • The Keyed Caesar cipher is a form of monoalphabetic substitution cipher.
  • The translation alphabet (the letters that are used instead of the ordinary alphabet) starts with the secret key. Each letter is only used once, so if a letter is used twice, only the first occurence is used. Then the translation alphabet is completed with the remaining letters in alphabetical order. Finally, it is shifted like an ordinary Caesar Cipher.
  • If the key is left blank, it behaves like an ordinary Caesar Cipher.
  • To improve obfuscation, spaces can be removed or replaced with a character, such as X, in the plaintext before encryption. Also the shift should not be zero.
  • A keyed Caesar cipher still be broken through frequency analysis.

Caesar cipher, and variants of it, are often used in easy geocaching mystery caches, and easy logic puzzles.

Sample Keyed Caesar Cipher

Code-breaking is not only fun, but also a very good exercise for your brain and cognitive skills. Why don’t you try breaking this example cipher:

im il aifx gn wgp mg ciae z lozkeokgu re kehciex bpm lpkecw wgp uicc mrifa dgke gn de uref wgp rezk mre lhcefxix mrgptrml dw feu bkzif il tgift mg mpkf gpm