Vigenère cipher (JavaScript)
Program
Description
This JavaScript program encrypts and decrypts messages using the Vigenère cipher. The key must have at least one letter. The key is case-insensitive and non-letters are ignored. When encrypting or decrypting, the case is preserved, and non-letters are unchanged. The Caesar cipher is a special case of the Vigenère cipher with a one-letter key.
The source code is available for viewing.