Netcetera 3DS SDK API

The API of the Netcetera 3DS SDK complies with the API defined by the EMVCo 3DS SDK Specification document. This section describes how the Netcetera 3DS SDK can be used to perform 3DS Authentication of payment or non-payment transactions.


First an instance of ThreeDS2ServiceSDK should be created. When creating the ThreeDS2ServiceSDK object, two constructors are available. One with a bundle argument and one without it. The default value for the bundle is Bundle.main. In case you want to specify a separate bundle for resources, pass the value using the ThreeDS2ServiceSDK(bundle:Bundle) constructor.


The 3DS Requestor App calls the initialize method at the start of the payment stage of a transaction. The app passes configuration parameters, UI configuration parameters, and user locale to this method. The ThreeDS2Service instance is unusable prior to the initialization.

In order to use the ThreeDS2Service for further actions, initialize it with ThreeDS2Service.initialize(...) method.

configParametersInstance of ConfigParameters. Before passing this parameter set the API key as described in API Key Configuration.
localeString that represents the locale for the app’s user interface.
uiCustomizationA [String: UiCustomization] dictionary where the String represents the UI appearance (DEFAULT or DARK) in which the UICustomization will be used. For more on how to create UICustomization take a look at the SDK Configuration page.
successA callback that is called when the initialization finishes successfully.
failureA callback that is called when the initialization finishes unsuccessfully. The failure callback takes an Error parameter that contains the failure details.


Note: There is an additional option for the integrator to initialize the SDK via a call without the success and failure callbacks. However, it is important to be mentioned that the method without callbacks is a blocking method. Therefore, it should be called on a background thread and should be handled as a long lasting operation in order to avoid UI unresponsiveness.

During initialization, security checks are performed and device information is collected. These parameters will be a part of the Authentication and will be provided to the ACS via 3DS Server for risk analysis.

For more details about the security checks and their handling, refer to Security Features.

For more details on the device data that is collected, refer to EMVCo 3DS SDK Device Info Specification.


After the security checks have been performed, the SDK provides the outcome as a list of Warning objects.

To obtain the result of these security checks call ThreeDS2Service.getWarnings().

Each of the resulting Warning objects has a Severity with value of LOW, MEDIUM and HIGH and it is up to the integrator to decide whether and how to act on each of them. For more details, please refer to Security Warnings.

The resulting warnings will be provided as part of the Device Info in the Authentication.


The 3DS Authentication flow starts with the authentication request that the 3DS Requestor Environment (Application or Library) sends to the 3DS Server. The 3DS Server uses that data to compose the AReq that is sent to the DS and further forwarded to the appropriate ACS.

The ACS evaluates the data provided in the AReq and responds with an ARes message to the DS, which then forwards the message to the 3DS Server. At the end, the 3DS Server communicates the result of the ARes message back to the 3DS Requestor Environment.

The 3DS SDK generates authentication parameters that should be used for building the initial Authentication Request. All these parameters should be sent to the 3DS Server, in a format defined by the 3DS Server API. These parameters can be retrieved from the Transaction object.

To obtain instance of Transaction, ThreeDS2Service.createTransaction(...) method can be used.

directoryServerIDThe ID of the Directory Server that will be used. Make sure that there is already a configuration for this DS added in DS Configuration
messageVersionProtocol version according to which the transaction shall be created. If nil, the latest supported protocol version by the SDK will be used.


After the Transaction object has been created, the AuthenticationRequestParameters can be obtained by calling Transaction.getAuthenticationRequestParameters().


The parameters that are part of the AuthenticationRequestParameters are defined in chapter 4.12 in the EMVCo 3DS SDK Specification.

While the Authentication Request is ongoing, a Processing Screen provided by the 3DS SDK shall be shown. To get instance of this processing screen use Transaction.getProgressView(...). For better user experience, the EMVCo 3DS Specification requires the processing screen to be shown for a minimum of two seconds, regardless of the authentication response time or result.

This requirement shall be implemented by the 3DS SDK integrator. For example, reference the Netcetera Demo Merchant application.

Starting the Challenge Flow

If the ACS assesses the transaction as high-risk, above certain threshold or that it requires higher level of authentication, it forces a Challenge Flow communication.

In case of Challenge Flow, the 3DS Requestor calls Transaction.doChallenge(...), and the SDK takes over the Challenge process.

Once a challenge has been started, invocation on Transaction.doChallenge(...) and Transaction.close() will result in SDK Runtime Error, but the Challenge Flow won't be interrupted nor the Transaction will be put in an invalid state. Once a result comes through the ChallengeStatusReceiver, calling of Transaction.doChallenge(...) and Transaction.close() is allowed if required.

challengeParametersInstance of ChallengeParameters created with values from the Authentication Response.
challengeStatusReceiverCallback object that implements ChallengeStatusReceiver. It will be notified about the challenge status.
timeOutTimeout interval (in minutes) within which the challenge process must be completed. The minimum timeout interval is defined to be 5 minutes.
inViewControllerThe view controller in which the challenge flow will be presented modally. This must not be a view controller that is presented. A presented view controller cannot present another view controller, so make sure the method is called with a correct parameter, otherwise the challenge view will not be shown.

Requestor App URL

Starting with version 2.2.0 of the EMV 3DS Specification Protocol, the application (requestor) integrating the 3DS SDK can be called from another (authentication) application during an OOB challenge flow to indicate completed OOB authentication. To use this feature, the requestor application should define its app url and provide it to the 3DS SDK.

The app url can be provided to the 3DS SDK in the challenge parameters via the setThreeDSRequestorAppURL(threeDSRequestorAppURL: String) method.

The passed URL should be a universal link that is configured for the application. The inclusion of this value in the challenge parameters is optional. If the app url is provided for an irrelevant version of the 3DS Specification Protocol (example version 2.1.0), the 3DS SDK will ignore it.

For further information on how to define the threeDSRequestorAppURL value, you can check the documents provided by EMVCo.

If the threeDSRequestorAppURL is set and the app is opened with this url in 2.2.0 transactions the OOB flow automatically continues. The transID query parameter in the URL must be the same as the current ongoing transaction. In this case the SDK knows that the authentication for that transaction has finished and can automatically send challenge request to the ACS.

In iOS the handling of events when the app was opened from a universal link is done in the main application delegate. In order for the SDK to be able to catch these events, the main application delegate needs to call the appropriate methods from ThreeDSSDKAppDelegate:

As an example on how to use and handle the app url on the application side, you can refer to the Netcetera Demo Merchant application.

Challenge Flow Results

After invoking Transaction.doChallenge(...), the Challenge Flow is started and the control of the UI is handed over to the 3DS SDK. The DS Requestor has the control back when any of the callback methods from the ChallengeStatusReceiver are invoked.

Implement a class that conform to the ChallengeStatusReceiver protocol.

When any of the callback methods of the ChallengeStatusReceiver are invoked, the challenge flow is considered finished. As a result, the 3DS SDK dismisses the challenge screen, closes the transaction, cleans up resources and gives the UI control over to the 3DS Requestor.

Closing of the Transaction

After the 3DS Authentication has finished, the 3DS Requestor should close the Transaction by calling Transaction.close() in order to clear references and avoid possible memory leaks.

This method should only be called when the Transaction.doChallenge(...) method is not called in a transaction. If invoked during an ongoing challenge, this method will throw SDK Runtime Error. At the end of the challenge flow, the 3DS SDK takes responsibility to cleanup resources and therefore this method is not required to be called.

After the transaction is closed and resources are cleaned up, any further operation on the Transaction object will result in a SDK Runtime Error.

Cleanup of the ThreeDS2Service

Similar to closing a Transaction, in order to free up resources which are used by the ThreeDS2Service, the ThreeDS2Service.cleanup() shall be used. Once an instance of ThreeDS2Service has freed up the used resources, the instance is in the same state as a newly created ThreeDS2Service and it can be used once again, though it should previously go through the Initialization process. After the ThreeDS2Service.cleanup() has been performed, previously created Transaction objects are in invalid state and shall not be used anymore. It is recommended to always create a new transaction object after initializing the service.

Objective-C class prefixes

To avoid conflicts of class/protocol names when using the SDK in Objective-C, all public classes and protocols of the SDK are prefixed with 'NCA'.

Example: NCAThreeDS2ServiceSDK, NCATransaction, NCAToolbarCustomization...

Note: This is only valid for Objective-C