Filters

Filters in NVIDIA FLARE are a type of FLComponent that has a process method to transform the Shareable object between the communicating parties. A Filter can be used to provide additional processing to shareable data before sending or after receiving from the peer.

The FLContext is available for the Filter to use.

class Filter(FLComponent, ABC):
    @abstractmethod
    def process(self, shareable: Shareable, fl_ctx: FLContext) -> Shareable:
        """Filter process applied to the Shareable object.

        Args:
            shareable: shareable
            fl_ctx: FLContext

        Returns:
            a Shareable object

        """
        pass

In config_fed_server.json and config_fed_client.json (for details see NVIDIA FLARE Application), task_result_filters and task_data_filters can be configured for processing data at the points highlighted in the image below:

Filters can convert data formats and a lot more. You can apply any type of massaging to the data for the purpose of security. In fact, privacy and homomorphic encryption techniques are all implemented as filters:

• ExcludeVars to exclude variables from shareable (nvflare.app_common.filters.exclude_vars)

• PercentilePrivacy for truncation of weights by percentile (nvflare.app_common.filters.percentile_privacy)

• SVTPrivacy for differential privacy through sparse vector techniques (nvflare.app_common.filters.svt_privacy)

• Homomorphic encryption filters to encrypt data before sharing (nvflare.app_common.homomorphic_encryption.he_model_encryptor.py and nvflare.app_common.homomorphic_encryption.he_model_decryptor)