Vigenère Cipher client-side ?
How to use Vigenère CipherThe Vigenère cipher is a polyalphabetic cipher: each letter of the message is shifted according to the matching letter of a repeated key. Unlike the Caesar cipher, which uses a single shift, Vigenère changes the shift at every letter, which makes it resistant to basic frequency analysis. Enter your text and a key, and the tool encrypts or decrypts instantly. You can keep the original case and punctuation, or keep only the letters.
Two variants are offered: the Beaufort cipher (where the key acts as an inverted reference) and autokey, where the key is extended by the plaintext itself to avoid periodic repetition. The alphabet is customizable. All processing is local in your browser — great for puzzles, treasure hunts and learning cryptography.
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The Vigenère cipher is a polyalphabetic cipher: each letter of the message is shifted according to the matching letter of a repeated key. Unlike the Caesar cipher, which uses a single shift, Vigenère changes the shift at every letter, which makes it resistant to basic frequency analysis. Enter your text and a key, and the tool encrypts or decrypts instantly. You can keep the original case and punctuation, or keep only the letters. Two variants are offered: the Beaufort cipher (where the key acts as an inverted reference) and autokey, where the key is extended by the plaintext itself to avoid periodic repetition. The alphabet is customizable. All processing is local in your browser — great for puzzles, treasure hunts and learning cryptography.
Encrypt and decrypt with Vigenère, Beaufort and autokey.
How to use Vigenère Cipher
The Vigenère cipher is a polyalphabetic cipher: each letter of the message is shifted according to the matching letter of a repeated key. Unlike the Caesar cipher, which uses a single shift, Vigenère changes the shift at every letter, which makes it resistant to basic frequency analysis. Enter your text and a key, and the tool encrypts or decrypts instantly. You can keep the original case and punctuation, or keep only the letters. Two variants are offered: the Beaufort cipher (where the key acts as an inverted reference) and autokey, where the key is extended by the plaintext itself to avoid periodic repetition. The alphabet is customizable. All processing is local in your browser — great for puzzles, treasure hunts and learning cryptography.
Frequently asked questions
How is it different from the Caesar cipher?
Caesar applies a single shift to every letter. Vigenère uses a key: each letter is shifted differently based on the key letter across from it, which is far harder to break.
What is autokey?
A variant where the (too short) key is extended by the plaintext itself instead of being repeated. This removes the periodicity that makes Vigenère breakable by the Kasiski method.
Is Vigenère secure today?
No, it is breakable by cryptanalysis (Kasiski examination, index of coincidence). It's a historical and educational cipher, not for protecting real data — use AES for that.