func decode(input: String, key: String) -> String {
        let inputBytes = input.utf8
        let keyBytes = key.utf8
        var keyIndex = 0

        var inputArray = [UInt8] (inputBytes)
        var keyArray = [UInt8] (keyBytes)

        for i in 0..<inputArray.count {
            print("input \(i) = \(inputArray[i])")
            print("key \(i) = \(keyArray[keyIndex])")
            inputArray[i] = inputArray[i] ^ keyArray[keyIndex]
            keyIndex = keyIndex + 1

            if (keyIndex == keyArray.count) {
                keyIndex = 0
            }
        }

        return String(bytes: inputArray, encoding: String.Encoding.utf8)!
    }