code: def _pkcs1imify(self, data):
          
          size = len(util.deflate_long(self.n, 0))
          filler = max_byte * (size - len(SHA1_DIGESTINFO) - len(data) - 3)
          return zero_byte + one_byte + filler + zero_byte + SHA1_DIGESTINFO + data
docs: turn a 20-byte SHA1 hash into a blob of data as large as the key's N,
          using PKCS1's \"emsa-pkcs1-v1_5\" encoding.  totally bizarre.