code: def hash_host(hostname, salt=None):
          
          if salt is None:
              salt = rng.read(SHA.digest_size)
          else:
              if salt.startswith('|1|'):
                  salt = salt.split('|')[2]
              salt = base64.decodestring(salt)
          assert len(salt) == SHA.digest_size
          hmac = HMAC.HMAC(salt, hostname, SHA).digest()
          hostkey = '|1|%s|%s' % (base64.encodestring(salt), base64.encodestring(hmac))
          return hostkey.replace('\n', '')
docs: Return a "hashed" form of the hostname, as used by openssh when storing
          hashed hostnames in the known_hosts file.
  
          @param hostname: the hostname to hash
          @type hostname: str
          @param salt: optional salt to use when hashing (must be 20 bytes long)
          @type salt: str
          @return: the hashed hostname
          @rtype: str