Now say you have an extra secret message to pass to your friend. You need something with a little more security than Caesar's cipher, so you choose to use Vigenere cipher, which, unlike the Caesar cipher, doesn't use a single numeric key, but instead uses a key word, each of whose characters represents a different key. A represents a shift with zero. It's the first letter of the alphabet, but we start counting at zero, not one. So B, the second letter of the alphabet represents a shift of one, C a shift of two, so on, and so forth. For instance, a keyword of dog represents three keys. Three, 14, and 6. And so were we to encrypt a word or message, we'd rotate the first letter of that word by three places, it's second letter by 14 places, and then it's third letter by six places. And if our message has more than three letters, then we'd use D again, then O again, then G again. All the while wrapping around from Z to A as needed. Allons-y, let's get cracking.