anchor.diff:  ;;; OFB mode
   
   (macrolet ((encrypt (cipher-specializer block-length-binding
  -					block-length-expr)
  +                                        block-length-expr)
                `(defmethod encrypt-with-mode ((cipher ,cipher-specializer)
                                               (mode ofb-mode) plaintext ciphertext
                                               plaintext-start plaintext-end
  
positive.code:                      finally (return-from decrypt-with-mode
                                 (let ((n-bytes-decrypted (- ciphertext-end ciphertext-start)))
                                   (values n-bytes-decrypted n-bytes-decrypted)))))))
  	   (message-length (cipher-specializer block-length-binding
  					       block-length-expr)
               (declare (ignore block-length-binding block-length-expr))
               `(defmethod encrypted-message-length ((cipher ,cipher-specializer)
                                                     (mode cfb8-mode) length
  
negative.code:                    finally (return-from encrypt-with-mode
                               (let ((n-bytes-encrypted (- plaintext-end plaintext-start)))
                                 (values n-bytes-encrypted n-bytes-encrypted)))))))
             (decrypt (cipher-specializer block-length-binding
                                                  block-length-expr)
               `(defmethod decrypt-with-mode ((cipher ,cipher-specializer)
                                              (mode cfb8-mode) ciphertext plaintext
  