Enter the numeric key and the text below and choose between encrypting and decrypting.
The Gronsfeld cipher is, just like the Vigenère cipher a polyalphabetic substitution. Characters are replaced using different alphabetic series and a key word is used for the encryption. The only difference is that the Gronsfeld cipher uses a numeric key. The Gronsfeld cipher can easily be converted to a Vigenère cipher by substitution of the key: 0=>a, 1=>b, ..., 9=>j.