code: def _GetServerCipher(self):
      
  
      if self.server_cipher is not None:
        expiry = self.server_cipher_age + rdfvalue.Duration("1d")
        if expiry > rdfvalue.RDFDatetime.Now():
          return self.server_cipher
  
      remote_public_key = self._GetRemotePublicKey(self.server_name)
      self.server_cipher = Cipher(self.common_name, self.private_key,
                                  remote_public_key)
      self.server_cipher_age = rdfvalue.RDFDatetime.Now()
      return self.server_cipher
docs: Returns the cipher for self.server_name.