Converters
Classic Cipher Converter
Encode and decode Morse code, ROT13, Caesar cipher, Vigenere cipher, and Atbash for puzzles, learning, CTF practice, and simple text obfuscation.
Tool
Encode and decode Morse code, ROT13, Caesar cipher, Vigenere cipher, and Atbash for puzzles, learning, CTF practice, and simple text obfuscation.
This tool runs in your browser. Your input is processed locally and is not uploaded.
About this Tool
Use this free online classic cipher converter for puzzle solving, classroom examples, CTF-style challenges, and understanding how historical substitution ciphers work. It includes Morse code, ROT13, Caesar shift, Vigenere keyword ciphers, and Atbash. Choose a cipher, switch between encode and decode, and provide the shift or keyword when the selected cipher needs one. These classic ciphers are not secure encryption and should not be used to protect sensitive data.
Examples
- HELLO → .... . .-.. .-.. --- in Morse code
- .... . .-.. .-.. --- → HELLO from Morse code
- hello → uryyb with ROT13
- uryyb → hello with ROT13
- attack → dwwdfn with Caesar shift 3
- dwwdfn → attack with Caesar shift 3
- ATTACKATDAWN → LXFOPVEFRNHR with Vigenere key LEMON
- abc xyz → zyx cba with Atbash
- SOS 123 → Morse code with letters and numbers
Frequently Asked Questions
Are classic ciphers secure encryption?
No. Morse, ROT13, Caesar, Vigenere, and Atbash are useful for puzzles, learning, and simple obfuscation, but they should not be used to protect sensitive data.
What is Morse code?
Morse code represents letters and numbers as dots and dashes. It is not an encryption system by itself, but it is often used in puzzles and training because it maps readable characters to signal patterns.
What is ROT13?
ROT13 is a Caesar-style substitution that shifts each letter by 13 positions. Because the alphabet has 26 letters, applying ROT13 twice returns the original text.
How does the Caesar cipher shift work?
A Caesar cipher shift moves each letter by a fixed number of positions in the alphabet. With shift 3, A becomes D, B becomes E, and so on.
What does the Vigenere keyword do?
The Vigenere cipher repeats the keyword across the message. Each keyword letter controls a different Caesar-style shift, so the same plaintext letter can encode to different ciphertext letters.
Why does Vigenere need the same key for decoding?
The keyword determines the sequence of shifts. Without the same keyword, the tool cannot know which shifts to reverse, so the decoded text will be wrong.
How does Atbash work?
Atbash reverses the alphabet: A maps to Z, B maps to Y, C maps to X, and so on. Encoding and decoding are the same operation.
What happens to spaces and punctuation?
For letter-based ciphers, spaces and punctuation are generally preserved so the text remains readable. Morse code uses spaces between letters and slashes between words where supported.
Can these ciphers handle numbers?
Morse code includes digits. Caesar, ROT13, Vigenere, and Atbash primarily transform letters and usually leave numbers unchanged.
When should I use this tool?
Use it for decoding puzzle text, checking challenge answers, teaching substitution ciphers, or quickly testing how a classic cipher transforms a message.