A polyalphabetic substitution cipher that uses a keyword to shift letters by different amounts. Each letter of the key determines the shift for the corresponding plaintext letter.

The keyword is repeated to match plaintext length. Each plaintext letter is shifted by the corresponding key letter's position (A=0, B=1, etc.). This creates varying shifts throughout.

Caesar uses one shift for all letters, making it easy to crack with frequency analysis. Vigenère's varying shifts mask letter frequencies, requiring the key length to be found first.

Use longer keywords (8+ characters) without repeating patterns. Avoid dictionary words and personal information. Random letter combinations are strongest.

Yes. Methods like Kasiski examination and index of coincidence can find key length. Once length is known, each position becomes a simple Caesar cipher. Not secure for real encryption.

A 26x26 grid showing all Caesar cipher alphabets. The row is the plaintext letter, column is the key letter, and intersection is the ciphertext. This tool calculates it automatically.

By default, spaces and punctuation pass through unchanged. You can optionally remove them for a more traditional ciphertext appearance.

No. Vigenère was broken in the 1800s and offers no real security. Use modern encryption (AES, RSA) for actual secret communication. This is for learning and puzzles only.

Numbers pass through unchanged by default. Only A-Z letters are encrypted. You can treat numbers as text by using their spelled-out names if needed.

Though named after Blaise de Vigenère, it was actually first described by Giovan Battista Bellaso in 1553. It was considered unbreakable for 300 years until Charles Babbage cracked it.

Vigenère Cipher

Encryption Breakdown

Vigenère Square

Key Strength

Sample Keywords

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