(defn enc [inputtext keytext]
  (loop [cryptoblock {}
         inputblock (.getBytes inputtext)
         keyval (reverse (.getBytes keytext))]
    (if (and inputblock)
      (recur (cons (bit-xor (first inputblock) (first keyval)) cryptoblock)
                   (next inputblock)
             (if (and (next keyval))
                (next keyval)
               (reverse (.getBytes keytext))))
             cryptoblock)))

(defn denc [cryptseq keytext]
  (loop [decrypt ""
         cryptseq (reverse cryptseq)
         keyval (reverse (.getBytes keytext))]
    (if (and cryptseq)
      (recur (format "%s%s" decrypt (char (bit-xor (first cryptseq) (first keyval))))
             (next cryptseq)
             (if (and (next keyval))
               (next keyval)
               (reverse (.getBytes keytext))))
      decrypt)))

(def abcd (enc "test" "abcd"))

(denc abcd "abcd")