Gronsfeld

This operates very similarly to a Vigenère cipher, but uses numbers instead of a key word.

The Gronsfeld cipher is essentially a Vigenère cipher, but uses numbers instead of letters in the key. So, a Gronsfeld key of 0123 is the same as a Vigenère key of ABCD. This online version lets you encode and decode messages with a keyed alphabet as well, to allow for maximum flexibility.

Examples: