Vigenère cipher

Encrypt and decrypt with the classic Vigenère polyalphabetic cipher — a teaching cipher, not real security.

Mode

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Classic Vigenère over A–Z: the key cycles per letter, other characters pass through untouched, and letter case is preserved. Text up to 300,000 characters. This is a classical cipher — it offers no real secrecy; do not use it to protect anything that matters.

How to use

  1. Choose encrypt or decrypt.
  2. Enter the key (letters only).
  3. Paste the text and read the result.

What it supports

Classic Vigenère over A–Z: the key cycles per letter, other characters pass through, letter case is preserved. Up to 300,000 characters. It offers no real secrecy — never use it to protect anything that matters.

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