Text Encryption Tool
Simple text encryption and decryption using Vigenere and Caesar ciphers with customisable passphrase and shift values
Warning: This tool uses basic educational encryption (Vigenere and Caesar ciphers). Do not use for protecting sensitive data. For real security, use modern encryption standards.
Use a memorable passphrase for both encryption and decryption.
Encrypt and decrypt text using classic cipher algorithms. Educational purposes only.
Two Classical Ciphers, Side by Side
Pick Vigenere or Caesar, type your plaintext, set a key (a passphrase for Vigenere, a number from 1 to 25 for Caesar), and hit Encrypt. The tool shifts each letter according to the cipher rules and outputs the ciphertext. Hit Decrypt with the same key to recover the original. The default Caesar shift is 3 (the original 'Caesar shift' that Julius Caesar reportedly used for military dispatches around 50 BC); Vigenere has no default and requires you to enter a passphrase.
Caesar shifts every letter by the same fixed amount. With shift 3, 'HELLO' becomes 'KHOOR' (H→K, E→H, L→O twice, O→R). Vigenere uses a repeating passphrase to vary the shift letter by letter. With key 'KEY', 'HELLO' becomes 'RIJVS' (H+K=R, E+E=I, L+Y=J, then the key repeats: L+K=V, O+E=S). Vigenere is much harder to crack by hand because the same plaintext letter can become different ciphertext letters depending on its position.
Why You Should Not Use This for Real Secrets
Both ciphers were broken decades or centuries ago. Caesar with 25 possible shifts can be brute-forced in under a second by trying every shift and looking for English words; the Kasiski examination cracks Vigenere given enough ciphertext (and a computer cracks it instantly with frequency analysis on the most likely key length). Modern attackers do not even bother running these as 'encryption' - they are puzzle-book ciphers, not security primitives.
If you need actual encryption for sensitive data, use AES-256 via a password manager (1Password, Bitwarden) or PGP for email. For password generation use the [password generator](/password-generator) and store the result in a manager. This tool is for educational purposes (learning how classical ciphers work), for puzzle creation (escape rooms, treasure hunts), and for low-stakes obfuscation (hiding spoilers in a forum post). Anything you would care about a stranger reading deserves real encryption.
Choosing Between Caesar and Vigenere for Puzzles
For a children's birthday party treasure hunt, use Caesar with shift 3 or shift 13 (ROT13). Kids can decode it with a paper alphabet wheel in a few minutes. For an adult escape room or a more challenging puzzle, use Vigenere with a 4 to 6 letter passphrase that is itself a clue (the room's theme, a date, a character's name). Decoding requires either knowing the key or doing the cryptanalysis, which takes a sharp adult 5 to 15 minutes with paper.
A worked example for a puzzle: encode the message 'THE NEXT CLUE IS UNDER THE BLUE BOOK' with Vigenere key 'BISHOP' to get a string of letters that means nothing without the key. Hide a clue elsewhere that points to BISHOP - a chess piece on a desk, a portrait of a bishop on the wall - and the puzzle solves itself. The [password generator](/password-generator) is useful for picking memorable but non-obvious keys when the plot calls for a random-looking password rather than a thematic one.
Frequently Asked Questions
What happens to numbers, spaces, and punctuation when I encrypt?
They pass through unchanged. The ciphers in this tool only operate on the 26 Latin letters (A-Z and a-z); digits, spaces, punctuation, and any other character appears in the ciphertext exactly as it does in the plaintext. That is a deliberate choice for puzzle-making but does leak information about the original (sentence boundaries, word lengths). For real encryption you want everything obfuscated.
Is the case preserved when I encrypt?
Yes. Uppercase letters in the plaintext stay uppercase in the ciphertext; lowercase stay lowercase. The shift maths uses the same offset either way, just based on different reference codepoints (65 for uppercase A, 97 for lowercase a). 'Hello' encrypted with Caesar shift 3 is 'Khoor', preserving the capital H.
What is ROT13 and is it the same as Caesar?
ROT13 is Caesar with shift 13. Because the alphabet has 26 letters, shifting by 13 twice brings you back to the original - so encrypting and decrypting are the same operation. ROT13 is the de facto standard for hiding spoilers, jokes, and answers in plain-text forums; this tool will produce ROT13 if you set the Caesar shift to 13.
Could a computer crack a Vigenere with a long passphrase?
Yes, given enough ciphertext. With a 6-letter key and 200+ characters of ciphertext, frequency analysis recovers the key in under a second on a laptop. Even a 12-letter random key falls to a determined attacker if they have a few thousand characters. Vigenere is unbreakable only when the key is at least as long as the message and never reused (the one-time pad), and that is impractical for almost everything.