(defun decrypt (ciphertext &optional (key 55665) (n 4) (c1 52845) (c2 22719))
  (loop :for i :from 0
        :for cipher :across ciphertext
        :for R := key :then (mod (+ c2 (* c1 (+ cipher R)))65536)
        :for P := (logxor cipher (ash R -8))
        :unless (< i n)
          :collect P))