code: def checkKey(self, credentials):
          
          filename = self._keyfile
          if not os.path.exists(filename):
              return 0
          lines = open(filename).xreadlines()
          for l in lines:
              l2 = l.split()
              if len(l2) < 2:
                  continue
              try:
                  if base64.decodestring(l2[1]) == credentials.blob:
                      return 1
              except binascii.Error:
                  continue
          return 0
docs: Retrieve the keys of the user specified by the credentials, and check
          if one matches the blob in the credentials.