class EthereumWorkOrderProxyImpl(WorkOrderProxy):
    """
    This class is meant to write work-order related data to Ethereum
    blockchain. Detailed method description is available in the interface
    """
    def __init__(self, config):
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def __validate(self, config):
        """
        Validates config parameters for existence.
        Returns false if validation fails and true if it succeeds
        """
        try:
            if config["ethereum"]["work_order_contract_file"] is None:
                logging.error("Missing work order contract file path!!")
                return False
            if config["ethereum"]["work_order_contract_address"] is None:
                logging.error("Missing work order contract address!!")
                return False
            if config["ethereum"]["provider"] is None:
                logging.error("Missing Ethereum provider url!!")
                return False
        except KeyError as ex:
            logging.error("Required configs not present".format(ex))
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.
        """
        self.__eth_client = EthereumWrapper(config)
        self._config = config
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["work_order_contract_file"]
        contract_address = \
            config["ethereum"]["work_order_contract_address"]
        self.__contract_instance, self.__contract_instance_evt =\
            self.__eth_client.get_contract_instance(
                contract_file_name, contract_address
            )

    def work_order_submit(self,
                          work_order_id,
                          worker_id,
                          requester_id,
                          work_order_request,
                          id=None):
        """
        Submit work order request
        work_order_id is a unique id to identify the work order request
        worker_id is the identifier for the worker
        requester_id is a unique id to identify the requester
        work_order_request is a json string(Complete definition at
        work_order.py interface file)
        Returns
            An error code, 0 - success, otherwise an error.
        """
        if (self.__contract_instance is not None):

            if not _is_valid_work_order_json(work_order_id, worker_id,
                                             requester_id, work_order_request):
                logging.error("Invalid request string {}"\
                    .format(work_order_request))
                return ERROR

            txn_dict = self.__contract_instance.functions.workOrderSubmit(
                work_order_id, worker_id, requester_id,
                work_order_request).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Exception as e:
                logging.error(
                    "Exception occured when trying to execute workOrderSubmit "
                    + "transaction on chain" + str(e))
                return ERROR
        else:
            logging.error("Work order contract instance is not initialized")
            return ERROR

    def work_order_complete(self, work_order_id, work_order_response):
        """
        This function is called by the Worker Service to
        complete a Work Order successfully or in error.
        This API is for proxy model.
        params
            work_order_id is unique id to identify the work order request
            work_order_response is the Work Order response data in string
        Returns
            An error code, 0 - success, otherwise an error.
        """
        if (self.__contract_instance is not None):

            txn_dict = self.__contract_instance.functions.workOrderComplete(
                work_order_id, work_order_response).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Exception as e:
                logging.error("Execption occured when trying to execute " +
                              "workOrderComplete transaction on chain" +
                              str(e))
                return ERROR
        else:
            logging.error("Work order contract instance is not initialized")
            return ERROR

    def start_work_order_completed_event_handler(self, evt_handler,
                                                 show_decrypted_output,
                                                 verification_key, session_key,
                                                 session_iv):
        """
        Function to start event handler for handling workOrderCompleted
        event from Ethereum blockchain
        """
        logging.info("About to start Ethereum event handler")

        # Start an event listener that listens for events from the proxy
        # blockchain, extracts response payload from there and passes it
        # on to the requestor

        w3 = BlockchainInterface(self._config)

        contract = self.__contract_instance_evt
        # Listening only for workOrderCompleted event now
        listener = w3.newListener(contract, "workOrderCompleted")

        try:
            daemon = EventProcessor(self._config)
            asyncio.get_event_loop().run_until_complete(
                daemon.start(listener, evt_handler, show_decrypted_output,
                             verification_key, session_key, session_iv))
        except KeyboardInterrupt:
            asyncio.get_event_loop().run_until_complete(daemon.stop())

    def encryption_key_retrieve(self,
                                worker_id,
                                last_used_key_nonce,
                                tag,
                                requester_id,
                                signature_nonce=None,
                                signature=None,
                                id=None):
        """
        Get Encryption Key Request Payload
        """
        pass

    def encryption_key_start(self, tag, id=None):
        """
        Function to inform the Worker that it should start
        encryption key generation for this requester.
        """
        pass

    def encryption_key_set(self,
                           worker_id,
                           encryption_key,
                           encryption_nonce,
                           tag,
                           signature,
                           id=None):
        """
        Set Encryption Key Request Payload
        """
        pass

    def work_order_get_result(self, work_order_id, id=None):
        """
        Get worker order result
        """
        pass

    def encryption_key_get(self,
                           worker_id,
                           requester_id,
                           last_used_key_nonce=None,
                           tag=None,
                           signature_nonce=None,
                           signature=None,
                           id=None):
        """
        Get Encryption Key Request Payload
        """
        pass
Exemple #2
0
class EthereumWorkerRegistryListImpl(WorkerRegistryList):
    """
    This class provide APIs to read/write registry entries of workers,
    which is stored in Ethereum blockchain.
    """
    def __init__(self, config):
        if self.__validate(config):
            self.__initialize(config)
        else:
            raise Exception("Invalid or missing config parameter")

    def registry_lookup(self, app_type_id=None):
        """
        Registry Lookup identified by application type id
        It returns following
        1. totalCount is the total number of entries matching a specified
        lookup criteria.  If this number is larger than the size of the ids
        array, the caller should use the lookupTag to call workerLookUpNext
        to retrieve the rest of the ids.
        2. lookupTag is an optional parameter. If it is returned, it means that
        there are more matching registry ids that can be retrieved by calling
        the function registry_lookup_next with this tag as an input parameter.
        3. ids is an array of the registry organization ids that match the
        input parameters
        Returns tuple containing count, lookup tag and list of organization
        ids on success and returns None on error.
        """
        if (self.__contract_instance is not None):
            if app_type_id is not None:
                if is_valid_hex_str(
                        binascii.hexlify(app_type_id).decode("utf8")):
                    lookupResult = \
                        self.__contract_instance.functions.registryLookUp(
                            app_type_id).call()
                else:
                    logging.info(
                        "Invalid application type id {}".format(app_type_id))
                    return None
            else:
                lookup_result = \
                    self.__contract_instance.functions.registryLookUp(b"") \
                    .call()
            return lookup_result
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None

    def registry_retrieve(self, org_id):
        """
        Retrieving Registry Information identified by organization id
        It returns tuple containing following on success.
        1. uri is string defines a URI for this registry that supports the
        Off-Chain Worker Registry JSON RPC API. It is going to be None
        for proxy model.
        2. sc_addr Ethereum address for worker registry smart contract
        address.
        3. application_type_ids list of application ids(array of byte[])
        4. status of the registry
        Returns None on error.
        """
        if (self.__contract_instance is not None):
            if (is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")) is
                    False):
                logging.info("Invalid Org id {}".format(org_id))
                return None
            else:
                registry_details = \
                    self.__contract_instance.functions.registryRetrieve(
                        org_id).call()
                return registry_details
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None

    def registry_lookup_next(self, app_type_id, lookup_tag):
        """
        Getting Additional Registry Lookup Results
        This function is called to retrieve additional results of the
        Registry lookup initiated by the registryLookUp call.
        Inputs
        1. application_type_id is an application type that has to be
        supported by the workers retrieved.
        2. lookup_tag is returned by a previous call to either this function
        or to registryLookUp.

        Outputs tuple on success containing the below.
        1. total_count is a total number of entries matching the lookup
        criteria. If this number is larger than the number of ids returned
        so far, the caller should use lookup_tag to call registry_lookup_next
        to retrieve the rest of the ids.
        2. new_lookup_tag is an optional parameter. If it is returned, it means
        that there are more matching registry ids that can be retrieved by
        calling this function again with this tag as an input parameter.
        3. ids is an array of the registry ids that match the input parameters
        Returns None on error.
        """
        if (self.__contract_instance is not None):
            if is_valid_hex_str(binascii.hexlify(app_type_id).decode("utf8")):
                lookup_result = \
                    self.__contract_instance.functions.registryLookUpNext(
                        app_type_id, lookup_tag).call()
                return lookup_result
            else:
                logging.info(
                    "Invalid application type id {}".format(app_type_id))
                return None
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None

    def __validate(self, config):
        """
        validates parameter from config parameters for existence.
        Returns false if validation fails and true if it success
        """
        if config["ethereum"]["direct_registry_contract_file"] is None:
            logging.error("Missing direct registry contract file path!!")
            return False
        if config["ethereum"]["direct_registry_contract_address"] is None:
            logging.error("Missing direct registry contract address!!")
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.
        """
        self.__eth_client = EthereumWrapper(config)
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["direct_registry_contract_file"]
        contract_address = \
            config["ethereum"]["direct_registry_contract_address"]
        self.__contract_instance = self.__eth_client.get_contract_instance(
            contract_file_name, contract_address)

    def registry_add(self, org_id, uri, sc_addr, app_type_ids):
        """
        Adding a new registry
        Inputs
        1. organization_id bytes[] identifies organization that hosts the
        registry, e.g. a bank in the consortium or anonymous entity.
        2. uri string defines a URI for this registry that supports
        the Off-Chain Worker Registry JSON RPC API.
        3. sc_addr bytes[] defines an Ethereum address that runs the
        Worker Registry Smart Contract API smart contract for this registry.
        4. app_type_ids []bytes[] is an optional parameter that defines
        application types supported by the worker managed by the registry.
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if (is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")) is
                    False):
                logging.info("Invalid Org id {}".format(org_id))
                return None
            if (sc_addr is not None and is_valid_hex_str(
                    binascii.hexlify(sc_addr).decode("utf8")) is False):
                logging.info("Invalid smart contract address {}")
                return None
            if (not uri):
                logging.info("Empty uri {}".format(uri))
                return None
            for aid in app_type_ids:
                if (is_valid_hex_str(binascii.hexlify(aid).decode("utf8")) is
                        False):
                    logging.info("Invalid application id {}".format(aid))
                    return None

            txn_dict = self.__contract_instance.functions.registryAdd(
                org_id, uri, org_id, app_type_ids).buildTransaction(
                    self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None

    def registry_update(self, org_id, uri, sc_addr, app_type_ids):
        """
        Update a registry
        Inputs
        1. organization_id bytes[] identifies organization that hosts the
        registry, e.g. a bank in the consortium or anonymous entity.
        2. uri string defines a URI for this registry that supports the
        Off-Chain Worker Registry JSON RPC API.
        3. sc_addr bytes[] defines an Ethereum address that runs a
        Worker Registry Smart Contract API smart contract for this registry.
        4. application_type_ids []bytes[] is an optional parameter that defines
        application types supported by the worker managed by the registry.
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if (is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")) is
                    False):
                logging.error("Invalid Org id {}".format(org_id))
                return None
            if (sc_addr is not None and is_valid_hex_str(
                    binascii.hexlify(sc_addr).decode("utf8")) is False):
                logging.error(
                    "Invalid smart contract address {}".format(sc_addr))
                return None
            if (not uri):
                logging.error("Empty uri {}".format(uri))
                return None
            for aid in app_type_ids:
                if (is_valid_hex_str(binascii.hexlify(aid).decode("utf8")) is
                        False):
                    logging.error("Invalid application id {}".format(aid))
                    return None

            txn_dict = \
                self.__contract_instance.functions.registryUpdate(
                    org_id, uri, sc_addr,
                    app_type_ids).buildTransaction(
                        self.__eth_client.get_transaction_params()
                        )
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None

    def registry_set_status(self, org_id, status):
        """
        Setting Registry Status
        Inputs
        1. organization_id bytes[] identifies organization that hosts the
        registry
        2. status defines registry status to set. The currently defined values
        are:
            1 - indicates that the registry is active
            2 - indicates that the registry is "off-line" (temporarily)
            3 - indicates that the registry is decommissioned
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if (is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")) is
                    False):
                logging.info("Invalid Org id {}".format(org_id))
                return None
            if not isinstance(status, RegistryStatus):
                logging.info("Invalid registry status {}".format(status))
                return None
            txn_dict = \
                self.__contract_instance.functions.registrySetStatus(
                    org_id,
                    status.value).buildTransaction(
                        self.__eth_client.get_transaction_params()
                        )
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "direct registry contract instance is not initialized")
            return None
Exemple #3
0
class EthereumWorkerRegistryImpl(WorkerRegistry):
    """
    This class is meant to set/get worker related information to/from Ethereum
    blockchain. Detailed method description is available in the interface.
    """

    def __init__(self, config):
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def worker_lookup(self, worker_type, org_id, application_id, id=None):
        """
        Initiating Worker lookup
        This function retrieves a list of Worker ids that match the input
        parameters.
        The Worker must match all input parameters (AND mode) to be included
        in the list.
        If the list is too large to fit into a single response (the maximum
        number of entries in a single response is implementation specific),
        the smart contract should return the first batch of the results
        and provide a lookupTag that can be used by the caller to
        retrieve the next batch by calling worker_lookup_next.

        All input parameters are optional and can be provided in any
        combination to select Workers.

        Inputs
        1. worker_type is a characteristic of Workers for which you may wish
        to search
        2. organization_id is an id of an organization that can be used to
        search for one or more Workers that belong to this organization
        3. application_type_id is an application type that is supported by
        the Worker

        Returns
        1. total_count is a total number of entries matching a specified
        lookup criteria. If this number is bigger than size of ids array,
        the caller should use lookupTag to call workerLookUpNext to
        retrieve the rest of the ids.
        2. lookup_tag is an optional parameter. If it is returned, it means
        that there are more matching Worker ids that can be retrieved by
        calling function workerLookUpNext with this tag as an input parameter.
        3. ids is an array of the Worker ids that match the input parameters.
        """

        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(org_id):
                logging.error("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(application_id):
                logging.error(
                    "Invalid application id {}".format(application_id))
                return None
            lookup_result = self.__contract_instance.functions.workerLookUp(
                worker_type.value, org_id, application_id).call()

            return _convert_lookup_result_to_json(lookup_result)
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_retrieve(self, worker_id, id=None):
        """
        Retrieve worker by worker id
        Inputs
        1. worker_id is the id of the registry whose details are requested.
        Returns:
        The same as the input parameters to the corresponding call to
        worker_register()
        plus status as defined in worker_set_status.
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None

            worker_details = self.__contract_instance.functions.workerRetrieve(
                worker_id).call()
            return _convert_retrieve_result_to_json(worker_details)
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_lookup_next(self, worker_type, org_id, application_id,
                           lookup_tag):
        """
        Getting Additional Worker Lookup Results
        Inputs
        1. worker_type is a characteristic of Workers for which you may wish
        to search.
        2. organization_id is an organization to which a Worker belongs.
        3. application_type_id is an application type that has to be supported
        by the Worker.
        4. lookup_tag is returned by a previous call to either this function
        or to worker_lookup.

        Returns:
        1. total_count is a total number of entries matching this lookup
        criteria.  If this number is larger than the number of ids returned
        so far, the caller should use lookupTag to call workerLookUpNext to
        retrieve the rest of the ids.
        2. new_lookup_tag is an optional parameter. If it is returned, it
        means that there are more matching Worker ids than can be retrieved
        by calling this function again with this tag as an input parameter.
        3. ids is an array of the Worker ids that match the input parameters.
        """

        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(org_id):
                logging.error("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(application_id):
                logging.error("Invalid application id {}".format(org_id))
                return None
            lookup_result = self.__contract_instance.functions\
                .workerLookUpNext(
                    worker_type.value,
                    org_id, application_id, lookup_tag).call()
            return lookup_result
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_register(self, worker_id, worker_type, organization_id,
                        application_type_ids, details):
        """
        Registering a New Worker
        Inputs
        1. worker_id is a worker id, e.g. an Ethereum address or
        a value derived from the worker's DID.
        2. worker_type defines the type of Worker. Currently defined types are:
            1. indicates "TEE-SGX": an Intel SGX Trusted Execution Environment
            2. indicates "MPC": Multi-Party Compute
            3. indicates "ZK": Zero-Knowledge
        3. organization_id is an optional parameter representing the
        organization that hosts the Worker, e.g. a bank in the consortium or
        anonymous entity.
        4. application_type_ids is an optional parameter that defines
        application types supported by the Worker.
        5. details is detailed information about the worker in JSON format as
        defined in
        https://entethalliance.github.io/trusted-computing/spec.html
        #common-data-for-all-worker-types
        Returns
        None - if registration does not succeed
        Transaction receipt - if registration succeeds
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(organization_id):
                logging.error("Invalid organization id {}"
                              .format(organization_id))
                return None
            for app_id in application_type_ids:
                if not is_valid_hex_str(app_id):
                    logging.error("Invalid application id {}".format(app_id))
                    return None
            # TODO : Validate worker details. As of now worker details are not
            # strictly following the spec
            """if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    logging.error(
                        "Worker details not valid : {}".format(is_valid))
                    return None
            """
            txn_dict = self.__contract_instance.functions.workerRegister(
                worker_id, worker_type.value, organization_id,
                application_type_ids, details)\
                .buildTransaction(
                self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(
                txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_update(self, worker_id, details):
        """
        Updating a Worker
        Inputs
        1. worker_id is a worker id, e.g. an Ethereum address or
        a value derived from the worker's DID.
        2. details is detailed information about the worker in JSON format
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None

            # TODO : Validate worker details. As of now worker details are not
            # strictly following the spec
            """if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    logging.error(
                        "Worker details not valid : {}".format(is_valid))
                    return None
            """
            txn_dict = self.__contract_instance.functions.workerUpdate(
                worker_id, details)\
                .buildTransaction(self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_set_status(self, worker_id, status):
        """
        Set the worker status identified by worker id
        Inputs
        1. worker_id is a worker id
        2. status defines Worker status. The currently defined values are:
            1 - indicates that the worker is active
            2 - indicates that the worker is "off-line" (temporarily)
            3 - indicates that the worker is decommissioned
            4 - indicates that the worker is compromised
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(status, WorkerStatus):
                logging.error("Invalid workerStatus {}".format(status))
                return None

            txn_dict = self.__contract_instance.functions.workerSetStatus(
                worker_id, status.value)\
                .buildTransaction(self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def _is_valid_json(self, json_string):
        try:
            json.loads(json_string)
        except ValueError as e:
            logging.error(e)
            return False
        return True

    def __validate(self, config):
        """
        validates parameter from config parameters for existence.
        Returns false if validation fails and true if it success
        """
        if config["ethereum"]["worker_registry_contract_file"] is None:
            logging.error("Missing worker registry contract file path!!")
            return False
        if config["ethereum"]["worker_registry_contract_address"] is None:
            logging.error("Missing worker registry contract address!!")
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.
        """
        self.__eth_client = EthereumWrapper(config)
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["proxy_worker_registry_contract_file"]
        contract_address = \
            config["ethereum"]["proxy_worker_registry_contract_address"]
        self.__contract_instance, self.__contract_instance_evt = \
            self.__eth_client.get_contract_instance(
                contract_file_name, contract_address
            )
Exemple #4
0
class EthereumWorkerRegistryImpl(WorkerRegistry):
    """
    This class is sets and gets worker-related information to and from
    the Ethereum blockchain.
    Detailed method descriptions are available in the WorkerRegistry
    interfaces.
    """
    def __init__(self, config):
        """
        Parameters:
        config    Dictionary containing Ethereum-specific parameters
        """
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def worker_lookup(self, worker_type, org_id, application_id, id=None):
        """
        Lookup a worker identified by worker_type, org_id, and application_id.
        All fields are optional and, if present, condition should match for
        all fields. If none are passed it should return all workers.

        If the list is too large to fit into a single response (the maximum
        number of entries in a single response is implementation specific),
        the smart contract should return the first batch of the results
        and provide a lookupTag that can be used by the caller to
        retrieve the next batch by calling worker_lookup_next.

        Parameters:
        worker_type    Optional characteristic of workers for which you may
                       wish to search
        org_id         Optional organization ID that can be used to search
                       for one or more workers that belong to this
                       organization
        application_id Optional application type ID that is supported by
                       the worker
        id             Optional JSON RPC request ID

        Returns:
        Tuple containing workers count, lookup tag, and list of
        worker IDs:
        total_count Total number of entries matching a specified
                    lookup criteria. If this number is larger than the
                    size of the IDs array, the caller should use
                    lookupTag to call worker_lookup_next to retrieve
                    the rest of the IDs
        lookup_tag  Optional parameter. If it is returned, it means
                    that there are more matching worker IDs, which can then
                    be retrieved by calling function worker_lookup_next
                    with this tag as an input parameter
        ids         Array of the worker IDs that match the input parameters

        On error returns None.
        """

        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(org_id):
                logging.error("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(application_id):
                logging.error(
                    "Invalid application id {}".format(application_id))
                return None
            lookup_result = self.__contract_instance.functions.workerLookUp(
                worker_type.value, org_id, application_id).call()

            return _convert_lookup_result_to_json(lookup_result)
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_retrieve(self, worker_id, id=None):
        """
        Retrieve the worker identified by worker ID.

        Parameters:
        worker_id  Worker ID of the registry whose details are requested
        id         Optional JSON RPC request ID

        Returns:
        Tuple containing worker status (defined in worker_set_status),
        worker type, organization ID, list of application IDs, and worker
        details (JSON RPC string).

        On error returns None.
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None

            worker_details = self.__contract_instance.functions.workerRetrieve(
                worker_id).call()
            return _convert_retrieve_result_to_json(worker_details)
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_lookup_next(self, worker_type, org_id, application_id,
                           lookup_tag):
        """
        Retrieve additional worker lookup results after calling worker_lookup.

        Parameters:
        worker_type         Characteristic of Workers for which you may wish
                            to search
        org_id              Organization ID to which a Worker belongs
        application_id      Optional application type ID that is
                            supported by the worker
        lookup_tag          is returned by a previous call to either this
                            function or to worker_lookup
        id                  Optional Optional JSON RPC request ID


        Returns:
        Tuple containing the following:
        total_count    Total number of entries matching this lookup
                       criteria.  If this number is larger than the number
                       of IDs returned so far, the caller should use
                       lookupTag to call worker_lookup_next to retrieve
                       the rest of the IDs
        new_lookup_tag Optional parameter. If it is returned, it
                       means that there are more matching worker IDs that
                       can be retrieved by calling this function again with
                       this tag as an input parameter
        ids            Array of the worker IDs that match the input parameters

        On error returns None.
        """

        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(org_id):
                logging.error("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(application_id):
                logging.error("Invalid application id {}".format(org_id))
                return None
            lookup_result = self.__contract_instance.functions\
                .workerLookUpNext(
                    worker_type.value,
                    org_id, application_id, lookup_tag).call()
            return lookup_result
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_register(self, worker_id, worker_type, organization_id,
                        application_type_ids, details):
        """
        Register a new worker with details of the worker.

        Parameters:
        worker_id       Worker ID value. E.g., an Ethereum address or
                        a value derived from the worker's DID
        worker_type     Type of Worker. Currently defined types are:
                        * "TEE-SGX": an Intel SGX Trusted Execution
                          Environment
                        * "MPC": Multi-Party Compute
                        * "ZK": Zero-Knowledge
        organization_id Optional parameter representing the
                        organization that hosts the Worker,
                        e.g. a bank in the consortium or
                        anonymous entity
        application_ids Optional parameter that defines
                        application types supported by the Worker
        details         Detailed information about the worker in
                        JSON RPC format as defined in
                https://entethalliance.github.io/trusted-computing/spec.html
                #common-data-for-all-worker-types

        Returns:
        Transaction receipt if registration succeeds.
        None if registration does not succeed.
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(worker_type, WorkerType):
                logging.error("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(organization_id):
                logging.error(
                    "Invalid organization id {}".format(organization_id))
                return None
            for app_id in application_type_ids:
                if not is_valid_hex_str(app_id):
                    logging.error("Invalid application id {}".format(app_id))
                    return None
            # TODO : Validate worker details. As of now worker details are not
            # strictly following the spec
            """if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    logging.error(
                        "Worker details not valid : {}".format(is_valid))
                    return None
            """
            txn_dict = self.__contract_instance.functions.workerRegister(
                worker_id, worker_type.value, organization_id,
                application_type_ids, details)\
                .buildTransaction(
                self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_update(self, worker_id, details):
        """
        Update a worker with details data.

        Parameters:
        worker_id  Worker ID value. E.g., an Ethereum address or
                   a value derived from the worker's DID
        details    Detailed information about the worker in JSON format

        Returns:
        Transaction receipt if registration succeeds.
        None if registration does not succeed.
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None

            # TODO : Validate worker details. As of now worker details are not
            # strictly following the spec
            """if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    logging.error(
                        "Worker details not valid : {}".format(is_valid))
                    return None
            """
            txn_dict = self.__contract_instance.functions.workerUpdate(
                worker_id, details)\
                .buildTransaction(self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_set_status(self, worker_id, status):
        """
        Set the worker status identified by worker ID.

        Parameters:
        worker_id Worker ID value. E.g., an Ethereum address or
                  a value derived from the worker's DID
        status    Worker status. The currently defined values are:
                  1 - worker is active
                  2 - worker is temporarily "off-line"
                  3 - worker is decommissioned
                  4 - worker is compromised

        Returns:
        Transaction receipt if registration succeeds.
        None if registration does not succeed.
        """

        if (self.__contract_instance is not None):
            if not is_valid_hex_str(worker_id):
                logging.error("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(status, WorkerStatus):
                logging.error("Invalid workerStatus {}".format(status))
                return None

            txn_dict = self.__contract_instance.functions.workerSetStatus(
                worker_id, status.value)\
                .buildTransaction(self.__eth_client.get_transaction_params())
            txn_receipt = self.__eth_client.execute_transaction(txn_dict)
            return txn_receipt
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def _is_valid_json(self, json_string):
        try:
            json.loads(json_string)
        except ValueError as e:
            logging.error(e)
            return False
        return True

    def __validate(self, config):
        """
        Validate configuration parameters for existence.

        Parameters:
        config    Ethereum-specific configuration parameters

        Returns:
        True if validation succeeds or false if validation fails.
        """
        if config["ethereum"]["worker_registry_contract_file"] is None:
            logging.error("Missing worker registry contract file path!!")
            return False
        if config["ethereum"]["worker_registry_contract_address"] is None:
            logging.error("Missing worker registry contract address!!")
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.

        Parameters:
        config    Ethereum-specific configuration parameters to initialize
        """
        self.__eth_client = EthereumWrapper(config)
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["proxy_worker_registry_contract_file"]
        contract_address = \
            config["ethereum"]["proxy_worker_registry_contract_address"]
        self.__contract_instance, self.__contract_instance_evt = \
            self.__eth_client.get_contract_instance(
                contract_file_name, contract_address
            )
class EthereumWorkerRegistryImpl(WorkerRegistry):
    """
    This class provide worker APIs which interact with
    Ethereum blockchain. Detail method description will be
    available in interface
    """
    def __init__(self, config):
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def worker_lookup(self, worker_type, org_id, application_id):
        """
        Lookup a worker identified worker_type, org_id and application_id
        all fields are optional and if present condition should match for all
        fields. If none passed it should return all workers.
        Returns tuple containing workers count, lookup tag and list of
        worker ids or on error returns None.
        """
        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.info("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")):
                logging.info("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(
                    binascii.hexlify(application_id).decode("utf8")):
                logging.info(
                    "Invalid application id {}".format(application_id))
                return None
            lookupResult = self.__contract_instance.functions.workerLookUp(
                worker_type.value, org_id, application_id).call()
            return lookupResult
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_retrieve(self, worker_id):
        """
        Retrieve the worker identified by worker id
        Returns tuple containing worker status, worker type,
        organization id, list of application ids and worker
        details(json string)
        On error returns None
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(worker_id).decode("utf8")):
                logging.info("Invalid worker id {}".format(worker_id))
                return None

            workerDetails = self.__contract_instance.functions.workerRetrieve(
                worker_id).call()
            return workerDetails
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_lookup_next(self, worker_type, org_id, application_id,
                           lookup_tag):
        """
        Getting Additional Worker Lookup Results
        Inputs
        1. worker_type is a characteristic of Workers for which you may wish
        to search.
        2. organization_id is an organization to which a Worker belongs.
        3. application_type_id is an application type that has to be supported
        by the Worker.
        4. lookup_tag is returned by a previous call to either this function
        or to worker_lookup.
        5. id is used for json rpc request

        Outputs tuple containing following.
        1. total_count is a total number of entries matching this lookup
        criteria.  If this number is larger than the number of ids returned
        so far, the caller should use lookupTag to call workerLookUpNext to
        retrieve the rest of the ids.
        2. new_lookup_tag is an optional parameter. If it is returned, it
        means that there are more matching Worker ids than can be retrieved
        by calling this function again with this tag as an input parameter.
        3. ids is an array of the Worker ids that match the input parameters.
        On error returns None.
        """
        if (self.__contract_instance is not None):
            if not isinstance(worker_type, WorkerType):
                logging.info("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(binascii.hexlify(org_id).decode("utf")):
                logging.info("Invalid organization id {}".format(org_id))
                return None
            if not is_valid_hex_str(
                    binascii.hexlify(application_id).decode("utf8")):
                logging.info("Invalid application id {}".format(org_id))
                return None
            lookupResult = self.__contract_instance.functions.workerLookUpNext(
                worker_type.value, org_id, application_id, lookup_tag).call()
            return lookupResult
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def __validate(self, config):
        """
        validates parameter from config parameters for existence.
        Returns false if validation fails and true if it success
        """
        if config["ethereum"]["worker_registry_contract_file"] is None:
            logging.error("Missing worker registry contract file path!!")
            return False
        if config["ethereum"]["worker_registry_contract_address"] is None:
            logging.error("Missing worker registry contract address!!")
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.
        """
        self.__eth_client = EthereumWrapper(config)
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["worker_registry_contract_file"]
        contract_address = \
            config["ethereum"]["worker_registry_contract_address"]
        self.__contract_instance = self.__eth_client.get_contract_instance(
            contract_file_name, contract_address)

    def worker_register(self, worker_id, worker_type, org_id, application_ids,
                        details):
        """
        Register new worker with details of worker
        Inputs
        1. worker_id is a worker id, e.g. an Ethereum address or
        a value derived from the worker's DID.
        2. worker_type defines the type of Worker. Currently defined types are:
            1. indicates "TEE-SGX": an Intel SGX Trusted Execution Environment
            2. indicates "MPC": Multi-Party Compute
            3. indicates "ZK": Zero-Knowledge
        3. organization_id is an optional parameter representing the
        organization that hosts the Worker, e.g. a bank in the consortium or
        anonymous entity.
        4. application_type_ids is an optional parameter that defines
        application types supported by the Worker.
        5. details is detailed information about the worker in JSON format as
        defined in
        https://entethalliance.github.io/trusted-computing/spec.html
        #common-data-for-all-worker-types
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(worker_id).decode("utf8")):
                logging.info("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(worker_type, WorkerType):
                logging.info("Invalid workerType {}".format(worker_type))
                return None
            if not is_valid_hex_str(binascii.hexlify(org_id).decode("utf8")):
                logging.info("Invalid organization id {}".format(org_id))
                return None
            for aid in application_ids:
                if not is_valid_hex_str(binascii.hexlify(aid).decode("utf8")):
                    logging.info("Invalid application id {}".format(aid))
                    return None
            if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    return None

            txn_statusn_hash = \
                self.__contract_instance.functions.workerRegister(
                    worker_id, worker_type.value, org_id, application_ids,
                    details).buildTransaction(
                        self.__eth_client.get_transaction_params()
                        )
            txn_status = self.__eth_client.execute_transaction(
                txn_statusn_hash)
            return txn_status
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_set_status(self, worker_id, status):
        """
        Set the registry status identified by worker id
        status is worker type enum type
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(worker_id).decode("utf8")):
                logging.info("Invalid worker id {}".format(worker_id))
                return None
            if not isinstance(status, WorkerStatus):
                logging.info("Invalid worker status {}".format(status))
                return None
            txn_statusn_hash = \
                self.__contract_instance.functions.workerSetStatus(
                    worker_id,
                    status.value).buildTransaction(
                        self.__eth_client.get_transaction_params()
                        )
            txn_status = self.__eth_client.execute_transaction(
                txn_statusn_hash)
            return txn_status
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None

    def worker_update(self, worker_id, details):
        """
        Update the worker with details data which is json string
        Updating a Worker
        Inputs
        1. worker_id is a worker id, e.g. an Ethereum address or
        a value derived from the worker's DID.
        2. details is detailed information about the worker in JSON format
        Returns transaction receipt on success or None on error.
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(worker_id).decode("utf8")):
                logging.error("Invalid worker id {}".format(worker_id))
                return None
            if details is not None:
                worker = WorkerDetails()
                is_valid = worker.validate_worker_details(details)
                if is_valid is not None:
                    logging.error(is_valid)
                    return None
            txn_statusn_hash = self.__contract_instance.functions.workerUpdate(
                worker_id, details).buildTransaction(
                    self.__eth_client.get_transaction_params())
            txn_status = self.__eth_client.execute_transaction(
                txn_statusn_hash)
            return txn_status
        else:
            logging.error(
                "worker registry contract instance is not initialized")
            return None
class EthereumWorkOrderProxyImpl(WorkOrderProxy):
    """
    This class is meant to write work-order related data to Ethereum
    blockchain. Detailed method description is available in the interface
    """
    def __init__(self, config):
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def __validate(self, config):
        """
        Validates config parameters for existence.
        Returns false if validation fails and true if it succeeds
        """
        if config["ethereum"]["proxy_work_order_contract_file"] is None:
            logging.error("Missing work order contract file path!!")
            return False
        if config["ethereum"]["proxy_work_order_contract_address"] is None:
            logging.error("Missing work order contract address!!")
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.
        """
        self.__eth_client = EthereumWrapper(config)
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["proxy_work_order_contract_file"]
        contract_address = \
            config["ethereum"]["proxy_work_order_contract_address"]
        self.__contract_instance = self.__eth_client.get_contract_instance(
            contract_file_name, contract_address)

    def _is_valid_work_order_json(self, work_order_id, worker_id, requester_id,
                                  work_order_request):
        """
        Validate following fields in JSON request against the ones
        provided outside the JSON - workOrderId, workerId, requesterId
        """
        json_request = json.load(work_order_request)
        if (work_order_id == json_request.get("workOrderId")
                and worker_id == json_request.get("workerId")
                and requester_id == json_request.get("requesterId")):
            return True
        else:
            return False

    def work_order_submit(self,
                          work_order_id,
                          worker_id,
                          requester_id,
                          work_order_request,
                          id=None):
        """
        Submit work order request
        work_order_id is a unique id to identify the work order request
        worker_id is the identifier for the worker
        requester_id is a unique id to identify the requester
        work_order_request is a json string(Complete definition at
        work_order.py interface file)
        Returns
            An error code, 0 - success, otherwise an error.
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(work_order_id).decode("utf8")):
                logging.error("Invalid work order id {}".format(work_order_id))
                return ERROR

            if not is_valid_hex_str(
                    binascii.hexlify(worker_id).decode("utf8")):
                logging.error("Invalid worker id {}".format(worker_id))
                return ERROR

            if not is_valid_hex_str(
                    binascii.hexlify(requester_id).decode("utf8")):
                logging.error("Invalid requester id {}".format(requester_id))
                return ERROR

            if not _is_valid_work_order_json(work_order_id, worker_id,
                                             requester_id, work_order_request):
                logging.error(
                    "Invalid request string {}".format(work_order_request))
                return ERROR

            txn_dict = self.__contract_instance.functions.workOrderSubmit(
                work_order_id, worker_id, requester_id,
                work_order_request).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Execption as e:
                logging.error(
                    "execption occured when trying to execute workOrderSubmit \
                     transaction on chain" + str(e))
                return ERROR
        else:
            logging.error("work order contract instance is not initialized")
            return ERROR

    def work_order_complete(self, work_order_id, work_order_response):
        """
        This function is called by the Worker Service to
        complete a Work Order successfully or in error.
        This API is for proxy model.
        params
            work_order_id is unique id to identify the work order request
            work_order_response is the Work Order response data in string
        Returns
            An error code, 0 - success, otherwise an error.
        """
        if (self.__contract_instance is not None):
            if not is_valid_hex_str(
                    binascii.hexlify(work_order_id).decode("utf8")):
                logging.error("Invalid work order id {}".format(work_order_id))
                return ERROR
            txn_dict = self.__contract_instance.functions.workOrderComplete(
                work_order_id, work_order_response).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Execption as e:
                logging.error("execption occured when trying to execute \
                     workOrderComplete transaction on chain" + str(e))
                return ERROR
        else:
            logging.error("work order contract instance is not initialized")
            return ERROR

    def encryption_key_retrieve(self,
                                worker_id,
                                last_used_key_nonce,
                                tag,
                                requester_id,
                                signature_nonce=None,
                                signature=None,
                                id=None):
        """
        Get Encryption Key Request Payload
        """
        pass

    def encryption_key_start(self, tag, id=None):
        """
        Function to inform the Worker that it should start
        encryption key generation for this requester.
        """
        pass

    def encryption_key_set(self,
                           worker_id,
                           encryption_key,
                           encryption_nonce,
                           tag,
                           signature,
                           id=None):
        """
        Set Encryption Key Request Payload
        """
        pass
class EthereumWorkOrderProxyImpl(WorkOrderProxy):
    """
    This class is meant to write work order-related data to the Ethereum
    blockchain.
    Detailed method descriptions are available in the interfaces.
    """
    def __init__(self, config):
        if self.__validate(config) is True:
            self.__initialize(config)
        else:
            raise Exception("Invalid configuration parameter")

    def __validate(self, config):
        """
        Validate configuration parameters for existence.

        Parameters:
        config    Configuration parameters

        Returns:
        True if validation succeeds or false if validation fails.
        """
        try:
            if config["ethereum"]["work_order_contract_file"] is None:
                logging.error("Missing work order contract file path!!")
                return False
            if config["ethereum"]["work_order_contract_address"] is None:
                logging.error("Missing work order contract address!!")
                return False
            if config["ethereum"]["provider"] is None:
                logging.error("Missing Ethereum provider url!!")
                return False
        except KeyError as ex:
            logging.error("Required configs not present".format(ex))
            return False
        return True

    def __initialize(self, config):
        """
        Initialize the parameters from config to instance variables.

        Parameters:
        config    Configuration parameters to initialize
        """
        self.__eth_client = EthereumWrapper(config)
        self._config = config
        tcf_home = environ.get("TCF_HOME", "../../../")
        contract_file_name = tcf_home + "/" + \
            config["ethereum"]["work_order_contract_file"]
        contract_address = \
            config["ethereum"]["work_order_contract_address"]
        self.__contract_instance, self.__contract_instance_evt =\
            self.__eth_client.get_contract_instance(
                contract_file_name, contract_address
            )

    def work_order_submit(self,
                          work_order_id,
                          worker_id,
                          requester_id,
                          work_order_request,
                          id=None):
        """
        Submit work order request to the Ethereum block chain.

        Parameters:
        work_order_id      Unique ID of the work order request
        worker_id          Identifier for the worker
        requester_id       Unique id to identify the requester
        work_order_request JSON RPC string work order request.
                           Complete definition at work_order.py and
                           defined in EEA specification 6.1.1.
        id                 Optional JSON RPC request ID

        Returns:
        0 on success and non-zero on error.
        """
        if (self.__contract_instance is not None):

            if not _is_valid_work_order_json(work_order_id, worker_id,
                                             requester_id, work_order_request):
                logging.error(
                    "Invalid request string {}".format(work_order_request))
                return ERROR

            txn_dict = self.__contract_instance.functions.workOrderSubmit(
                work_order_id, worker_id, requester_id,
                work_order_request).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Exception as e:
                logging.error("Exception occurred when trying to execute " +
                              "workOrderSubmit transaction on chain " + str(e))
                return ERROR
        else:
            logging.error("Work order contract instance is not initialized")
            return ERROR

    def work_order_complete(self, work_order_id, work_order_response):
        """
        This function is called by the Worker Service to
        complete a work order successfully or in error.
        This API is for the proxy model.

        Parameters:
        work_order_id       Unique ID to identify the work order request
        work_order_response Work order response data in a string

        Returns:
        errorCode           0 on success or non-zero on error.
        """
        if (self.__contract_instance is not None):

            txn_dict = self.__contract_instance.functions.workOrderComplete(
                work_order_id, work_order_response).buildTransaction(
                    self.__eth_client.get_transaction_params())
            try:
                txn_receipt = self.__eth_client.execute_transaction(txn_dict)
                return SUCCESS
            except Exception as e:
                logging.error("Execption occurred when trying to execute " +
                              "workOrderComplete transaction on chain " +
                              str(e))
                return ERROR
        else:
            logging.error("Work order contract instance is not initialized")
            return ERROR

    def work_order_get_result(self, work_order_id, id=None):
        """
        Query blockchain to get a work order result.
        This function starts an event handler for handling the
        workOrderCompleted event from the Ethereum blockchain.

        Parameters:
        work_order_id Work Order ID that was sent in the
                      corresponding work_order_submit request
        id            Optional JSON RPC request ID

        Returns:
        Tuple containing work order status, worker id, work order request,
        work order response, and error code.
        None on error.
        """
        logging.info("About to start Ethereum event handler")

        # Start an event listener that listens for events from the proxy
        # blockchain, extracts response payload from there and passes it
        # on to the requestor

        w3 = BlockchainInterface(self._config)

        contract = self.__contract_instance_evt
        # Listening only for workOrderCompleted event now
        listener = w3.newListener(contract, "workOrderCompleted")

        try:
            daemon = EventProcessor(self._config)
            # Wait for the workOrderCompleted event after starting the
            # listener and handler
            event = asyncio.get_event_loop()\
                .run_until_complete(daemon.get_event_synchronously(
                    listener, is_wo_id_in_event, wo_id=work_order_id))

            # Get the first element as this is a list of one event
            # obtained from gather() in ethereum_listener
            work_order_response = event[0]["args"]["workOrderResponse"]

            return json.loads(work_order_response)
        except KeyboardInterrupt:
            asyncio.get_event_loop().run_until_complete(daemon.stop())

    def encryption_key_retrieve(self,
                                worker_id,
                                last_used_key_nonce,
                                tag,
                                requester_id,
                                signature_nonce=None,
                                signature=None,
                                id=None):
        """
        Get Encryption Key Request Payload.
        Not supported for Ethereum.
        """
        pass

    def encryption_key_start(self, tag, id=None):
        """
        Inform the Worker that it should start
        encryption key generation for this requester.
        Not supported for Ethereum.
        """
        pass

    def encryption_key_set(self,
                           worker_id,
                           encryption_key,
                           encryption_nonce,
                           tag,
                           signature,
                           id=None):
        """
        Set Encryption Key Request Payload.
        Not supported for Ethereum.
        """
        pass

    def encryption_key_get(self,
                           worker_id,
                           requester_id,
                           last_used_key_nonce=None,
                           tag=None,
                           signature_nonce=None,
                           signature=None,
                           id=None):
        """
        Get Encryption Key Request Payload.
        Not supported for Ethereum.
        """
        pass