(define (pre-process-complete-padding data)
  (letrec ([add-the-bit-1-and-7-zeroes
            (λ (x)
              (bytes-append
               x
               (bytes (arithmetic-shift 1 7))))]
           [complete-padding
            (λ (x)
              (if (= (modulo (bytes-length-in-bits x) 512) 448)
                  x
                  (complete-padding (bytes-append x (bytes 0)))))])
    (complete-padding (add-the-bit-1-and-7-zeroes data))))