anchor.diff:  
   ;;; internal entry points to assure speed
   (defgeneric encrypt-with-mode (cipher mode plaintext ciphertext
  -                                      &key plaintext-start
  -                                      plaintext-end
  -                                      ciphertext-start
  -                                      handle-final-block)
  +                                      plaintext-start plaintext-end
  +                                      ciphertext-start handle-final-block)
     (:documentation "Encrypt PLAINTEXT, beginning at PLAINTEXT-START and
   continuing until PLAINTEXT-END, according to CIPHER in mode MODE.  Place
   the result in CIPHERTEXT, beginning at CIPHERTEXT-START.  PLAINTEXT and
  
positive.code:                                :end1 ,block-length-expr
                                 :start2 plaintext-start)
                        (encrypt-with-mode cipher sub-mode plaintext ciphertext
                                           :plaintext-start plaintext-start
                                           :plaintext-end plaintext-end
                                           :ciphertext-start ciphertext-start)
                        (setf buffer-index 0)
                        (decf plaintext-length amount)
                        (incf plaintext-start amount)
  
negative.code:                      with encrypted-iv of-type (simple-octet-vector ,(if (constantp `,block-length-expr)
                                                                           `,block-length-expr
                                                                           '*)) = (encrypted-iv mode)
                       with encrypt-function of-type function = (encrypt-function cipher)
                       for i from ciphertext-start below ciphertext-end
                       for j from plaintext-start
  